EPA
United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
EPA/600/6-88 AH 0
May 1986
Research and Development
Qualitative Pathogen
Risk Assessment for
Ocean Disposal of
Municipal Sludge
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EPA/600/6-88/010
May 1986
Qualitative Pathogen Risk Assessment for
Ocean Disposal of Municipal Sludge
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC 20460
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DISCLAIMER
This document has been reviewed in accordance with the U.S. Environ-
mental Protection Agency policy and approved for publication. Mention of
trade names or commercial products does not constitute endorsement or recom-
mendation for use.
ii
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PREFACE
Municipal wastewater sludges contain a wide variety of bacteria, viruses,
protozoa, helminths and fungi. These pathogens have the potential to cause
risks to human health after ocean disposal of sludge. Predictions of viral
and bacterial decay following ocean disposal of sludge 1s required for
assessing risks associated with potential transport of microorganisms.
Background Information on pathogens of concern and their persistence In
marine environments Is presented, concluding with a qualitative discussion of
the potential risks to human health. The literature search conducted Is
current as of 1986. The first draft of this document was prepared by the
University of Cincinnati under Cooperative Agreement No. CR13569010.
111
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DOCUMENT DEVELOPMENT
L. Fradkln, Document Manager
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH
Dr. S.M. Goyal, Author
Department of Virology and Epidemiology
University of Minnesota
St. Paul, MN
Dr. C. Gerba, Author
Department of Microbiology and Immunology
University of Arizona
Tucson, AZ
Dr. P.V. Scarplno, Co-Document Manager
C1v1l and Environmental Engineering Department
University of Cincinnati
Cincinnati, OH
Scientific Revlewer(s)
Dr. C.A. Brunner
Wastewater Research Division
Water Engineering Research Laboratory
Office of Environmental Engineering
and Technology Demonstration
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH
Dr. R. Caspe, Director
Water Management Division
Region 2
U.S. Environmental Protection Agency
New York, NY
Dr. R.R. Colwell
Vice President for Academic Affairs
and Professor of Microbiology
The University of Maryland
College Park, MD
Dr. A.P. Dufour, Chief
Microbiology Branch
Health Effects Research Laboratory
Office of Health Research
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH
Dr. N. Kowal
Health Effects Research Laboratory
Office of Health Research
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH
1v
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Scientific Reviewer(s) (continued)
Dr. V. Ol1ver1
School of Public Health
Johns Hopkins University
Baltimore, MD
Or. A. Rubin, Chief
Wastewater Sol Ids Criteria Branch
Criteria and Standards Division
Office of Water Regulations and Standards
Office of Water
U.S. Environmental Protection Agency
Washington, DC
Dr-.-R.W. Zeller
Senior Science Advisor
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
Washington, DC
Technical Editor
Judith A. Olsen
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Cincinnati, OH
Document Preparation
Technical Support Services Staff: Patricia A. Daunt, Bette L. Zwayer and
Jacqueline Bohanon, Environmental Criteria and Assessment Office, Cincinnati
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TABLE OF CONTENTS
Page
1. INTRODUCTION. . . . 1-1
2. SLUDGE CHARACTERISTICS AND DISPOSAL METHODS 2-1
2.1. SLUDGE CHARACTERISTICS 2-1
2.2. DISPOSAL METHODS 2-1
2.3. SITE CONDITIONS AT OPERATED DISPOSAL SITES 2-2
2.3.1. New York Bight Dump Site 2-4
2.3.2. Philadelphia Dump Site 2-7
2.3.3. The 106-Mile Deep Water SHe 2-11
3. PATHOGENS OF CONCERN. . . . • 3-1
3.1. VIRUSES 3_1
3.2. BACTERIA 3_6
3.2.1. Salmonella 3-6
3.2.2. Shlgella 3-9
3.2.3. Fecal Indicator Bacteria 3-10
3.2.4. EscheMchla coll. 3-10
3.2;5. Vibrio cholerae 3-11
3.2.6. Vibrio parahemolytlcuj 3-12
3.2.7. Campylobacter 3_12
3.2.8. Yers1n1a 3-13
3.2.9. Pleslomonas shlgelloldes 3-13
3.2.10. Hycobacterlum 3-14
3.2.11. Leptosplra 3-15
3.2.12. Aeromonas hydrophlla 3-16
3.3. PROTOZOA 3-17
3.3.1. Entamoeba histolvtica . 3-17
3.3.2. G1ard1a lamblla 3-18
3.3.3. Acanthamoeba 3-19
3.4. HELMINTHS 3_22
3.4.1. Ancyclostoma 3-22
3.4.2. Ascarls 1umbr1co1des 3-23
3.4.3. Tr1chur1s trlchlura 3-24
3.4.4. Taenla 3-24
4. SECONDARY RISKS FROM MICROORGANISMS 4-1
4.1. DRUG RESISTANCE AND PLASMID TRANSFER 4-1
4.2. STIMULATION OF NATIVE MARINE PATHOGENS 4-3
4.3. OPPORTUNISTIC BACTERIA 4-4
4.4. GENETICALLY ENGINEERED ORGANISMS 4-5
v1
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TABLE OF CONTENTS (c'ont.)
5. EXPOSURE PATHWAYS .• .
6. PERSISTENCE OF PATHOGENS IN THE MARINE ENVIRONMENT. .......
6.1.
6.2.
6.3.
MARINE WATER . . . . • .
6.1.1. Bacteria
6.1.2. Enteric Viruses
6.1.3. Protozoa -
6.1.4. Helminths .....
SEDIMENTS
6.2.1. Bacteria. . .
6.2.2. Viruses
FISH AND SHELLFISH
6.3.1. Bacteria
6.3.2. Viruses
7. INFECTIVE DOSE FOR MICROORGANISMS
7.1.
7.2.
MINIMUM INFECTIVE DOSE
ESTIMATED MORBIDITY AND MORTALITY FOR ENTERIC PATHOGENS. .
8. SETTLING AND DISPERSAL OF SLUDGES DURING DISPOSAL
8.1.
8.2.
SHALLOW DUMP SITES
106-MILE DEEP WATER SITE ...... ...
9. QUALITATIVE RISK ASSESSMENT
9.1.
9.2.
9.3.
MARINE FOODS RISK ASSESSMENT
AEROSOL PATHWAY RISK ASSESSMENT
CONTACT EXPOSURE RISK ASSESSMENT
10. SUMMARY AND CONCLUSIONS
11. REFERENCES
Page
5-1
6-1
6-3
6-3
6-10
6-12
6-12
6-13
6-13
6-17
6-18
6-18
6-21
7-1
7-2
7-6
8-1
8-2
8-5
9-1
9-1
9-2
9-3
10-1
11-1
V11
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LIST OF TABLES
No.
2-1
2-2
2-3
2-4
3-1
3-2
3-3
6-1
7-1
7-2
9-1
9-2
Title
Isolation of Human Enterovlruses from New York Bight
Dump Site 2-5
Quantity of Sludge Disposed at Philadelphia Dump Site .... 2-8
Isolation of Viruses from Philadelphia Dump Site
and the Transect to the New York Bight 2-10
Temperature Ranges Observed in Relation to Depth at the
Philadelphia Sewage Sludge Dump Site (1983) 2-12
Enteric Viruses That Hay Be Present in
Sewage and Sludge 3-3
Newly Recognized Viruses That Can Be Transmitted
by Water 3-4
Bacteria and Parasites Pathogenic to Han That
Hay Be Present In Sewage and Sludge 3-7
Reported Populations of Bacteria in Water and Sediment. ... 6-15
Contributors to Uncertainty 1n Determining Hlnimum
Infectious Dose for Enteric Viruses
7-3
7-9
Hortallty Rates for Enteric Bacteria and Enterovlruses. . . .
Estimated Die-Off Rates of Enteric Viruses in Seawater,
Sediments and Shellfish at Various Temperatures 9-6
Estimated Time Required for Complete Die-Off of Conforms
and Enterovlruses at the Philadelphia Dump Site 9-7
V111
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LIST OF FIGURES
No.
2-1
3-1
5-1
7-1
7-2
7-3
Title
Page
Sludge Disposal Sites In the North Atlantic . . 2-3
Average Annual Number of Waterborne-Dlsease Outbreaks,
1920-1980 ... ........ 3-2
Potential Pathways of Enteric Pathogen Transport 1n
the Marine Environment 5-2
Secondary Attack Rates of Enteric Viruses .......... 7-5
Percent of Individuals with Clinical Features for
Polio and Hepatitis Virus by Age 7-7
Frequency of Symptomatic Infections . . 7-8
1x
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LIST OF ABBREVIATIONS AND SYMBOLS
ATM
HAV.
MAIS
HID
HPN
PFU
sp.
spp.
*50
TCID50
Atmosphere
Hepatitis A virus
Mycobacterlum av1uin-1ntracenulare-scrofulaceum
Minimum Infectious dose
Most probable number
Plague-forming units
Species (singular)
Species (plural)
Time for 50% 1nact1vat1on
Time for 90% 1nact1vat1on
Time for 99% 1nact1vat1on
Dose at which 50% of Inoculated tissue cultures are Infected
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1. INTRODUCTION
Densely populated coastal regions of the United States generate large
quantities of domestic sewage and sludge. These wastes are often disposed
of directly Into the marine environment through coastal outfalls or> by
dumping from barges. In the latter case sewage sludge and/or Industrial
wastes are barged several miles offshore and discharged at a specific dump
site 1n open ocean waters. In the United States such sites Include or
Included the Philadelphia dump site (closed In 1980), the New York Bight
site (closed 1n 1988), the Puerto Rico Trench dump site (closed) and the
106-mile deep water ocean waste disposal site 1n the mid-Atlantic Bight
(which opened 1n March 1986 on a 5-year Interim basis).
A large amount of sludge has been dumped at such designated dump sites
around the world. In the United States, the first ocean dumping of sludge
occurred 1n 1924 1n the New York Bight. The amount of sludge dumped Into
the ocean by U.S. municipalities and Industries 1n the 1970s was estimated
to be 4.5 million wet metric tons per year. In 1977, the U.S. Congress
enacted Public Law No. 95-153 amending the Marine Protection, Research and
Sanctuaries Act of 1972. The 1977 Amendment prohibits the dumping after
December 31, 1981, of any sewage sludge that would be harmful to the marine
ecosystem and human health.
Although the concentration of enteric microorganisms Is rapidly reduced
In receiving waters as a result of dilution, dispersion, sedimentation and
degradation, microorganisms may survive long enough to pose certain hazards
to human health and the marine ecosystem. The accumulation of heavy metals,
pathogens and persistent organic compounds In sediment and shellfish may
create Insidious reservoirs potentially hazardous to public health. The
risks posed by the pollution of the marine environment Include exposure of
1-1
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the public to pathogenic microorganisms through primary contact recreation
such as bathing, scuba and skin diving, watersk11ng and during occupational
activities such as commercial and military diving operations. Exposure, of
course, depends upon the proximity of the disposal site to the recreational
area.
In addition, 1ngest1on of raw or partially cooked bivalve mollusks such
as oysters and clams that have become contaminated also may be hazardous to
human health. Hollusks are of particular concern since they feed by filter-
Ing partlculate matter, Including microorganisms, from large volumes of sea-
water. When used for human consumption, they are often eaten raw, that 1s,
the whole animal Including the Intestinal tract Is Ingested (Gerba and Goyal,
1978).
It should be pointed out that some of, the pathogens present 1n sewage may
cause Infection not only through Ingestion but also by Inhalation of dust or
aerosol droplets. Since aerosols can travel long distances, this fact should
not be overlooked. It should also be realized that some pathogens, such as
hookworms, can penetrate through the skin, whereas others (adenovirus, for
example) may enter through the eye after rubbing the eye with contaminated
fingers or by direct exposure of eyes during swimming.
The present assessment focuses on mlcrobial contaminants of municipal
wastewater sludges that have been actually or potentially Implicated In
producing human Illness; it summarizes available data on the occurrence,
transport and fate of these pathogens 1n the marine environment, and
describes the possible hazards to human health associated with the disposal
of sludges In open ocean waters. Following the presentation of background
Information, a discussion of risks associated with ocean disposal of sludge
,are presented. The scope of the risk assessment is restricted, therefore, to
pathogens present 1n sewage sludge discharged at the open ocean dump sites.
1-2
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2. SLUDGE CHARACTERISTICS AND DISPOSAL METHODS
Before the risks associated with ocean dumping of sludge can be evalu-
c
ated, 1t 1s Important to review sludge characteristics that might determine
the dispersion and survival of sewage pathogens.
2.1. SLUDGE CHARACTERISTICS
Sewage sludge 1s a complex mixture of solids of biological and mineral
origin that are removed from wastewater in sewage treatment plants. Sludge
is a by-product of physical (primary treatment), biological (activated
sludge, trickling filters) and physiochemical (chemical precipitation with
Ume, ferric chloride or alum) treatment of wastewater. Many of the patho-
genic microorganisms that are present in raw wastewaters will find their way
Into sewage sludges. Treatment of these sludges by anaerobic digestion
and/or dewatering will reduce the number of pathogens, but significant num-
bers may remain (Goddard et al., 198?; Goyal et al., 1984b). The type of
treatment will determine the concentration of pathogens and the relative
risk of disposal.
Stabilization of sludges, together with significant pathogen reduction,
may be accomplished by either aerobic or anaerobic digestion, lime addition,
heat, wet oxidation or incineration.
Sludges may be dewatered by a number of processes including drying beds,
vacuum filtration, pressure filtration, centrlfugation and heat drying.
Usually chemicals such as alum, lime, ferric chloride or synthetic poly-
electrolytes are added to Improve the dewatering characteristics of the
sludge.
2.2. DISPOSAL METHODS ' f
The disposal of sewage and sludge in the marine environment is accom-
plished by construction of offshore sewage outfalls or by barging the sludge
2-1
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several miles offshore and then discharging 1t at a designated dump site on
or at the edge of the continental shelf.
Submarine offshore sewage outfalls are sometimes used to convey treated
effluent out to sea for disposal. It 1s assumed that discharging sewage by
this method results 1n reduced pollution of adjacent beaches. However,
shoreward eddies, wind and wave action may cause waste plumes to Intersect
bathing waters along adjacent shorelines. Offshore outfalls have been shown
to discharge a large number of bacteria and viruses 1n marine waters. Vasl
et al. (1981) were able to detect fecal Indicator bacteria and viruses up to
5 km from the sewage discharge point 1n the seawater. The principal method
by which sewage sludge 1s discharged Into the sea 1s simply to dump sludge
Into a barge, tow the barge to the disposal site, open disc valves fixed 1n
the bottom of specially constructed holding tanks In the hull of the barge
and allow the sludge to drift away. The sludge may be dumped from a moving
barge (line dump) or from a stationary barge (spot dump). Obviously,
greater dilution will take place when a line dump,1s made rather than a spot
dump (see Chapter 8 for sludge dispersal).
2.3. SITE CONDITIONS AT OPERATED DISPOSAL SITES
There are or were several dump sites 1n open ocean waters 1n the United
States (Figure 2-1). These Include the Philadelphia sewage sludge dump site
(closed 1n 1980) (O'Malley et al., 1982), the New York Bight (to be closed
1n 1988), the Puerto Rico Trench dump site (closed) (Peele et al., 1981) and
the 106-mile deep water ocean waste disposal site (White et al., 1980). The
Puerto R1co Trench dump site was used primarily for pharmaceutical wastes
and 1s now closed for dumping. In Its place, an outfall has now been
Installed that carries sewage effluent from a treatment plant at AMcebo,
Puerto R1co. Open ocean dump sites may be used for the
2-2
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41'
40
o
39C
38e
ONG ISLAND SOUND
1. NEW YORK BIGHT
SLUDGE SITE
2. NEW YORK BIGHT
ALTERNATE SLUDG
SITE
3. 106-MILE SITE ',
4. PHILADELPHIA
SLUDGE SITE
• • ".
• * * *
NEW JERSEY"
NAUTICAL MILES
FIGURE 2-1
Sludge Disposal Sites 1n the North Atlantic
Source: Goyal et al., 1984a
2-3
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disposal of the following: Industrial waste, dredged material, sewage
sludge and radioactive waste. The following assessment covers only sewage
sludge disposal sites.
:Il
To understand fully the effects of ocean dumping, 1t Is Important to
characterize the environment as well as the wastes being dumped.
2.3.1. New York Bight Dump Site. The New York Bight dump site will cease
to be used for dumping of municipal sludge In 1988. In the United States,
the first ocean dumping of sludge occurred 1n 1924 1n the New York Bight.
The New York Bight dump site, also known as the 12-mile site, 1s a coastal
ocean area at the apex of New Jersey and Long Island and 1s situated roughly
12 miles (19.2 km) equal distance from the shores of New York and New Jersey
at the entrance to the Hudson Canyon. This site has been used for sludge
disposal since 1924, but dredge spoil has also been discharged 1n this
area. The sludge dumping area occupies 100 km2 and 1s located at latitude
40°25I04"N and longitude 73°44'53"W. The depth at the dump site 1s -30 m.
During 1965-1970, the average annual Input of sludge to the New York Bight
was 3.2xl09 kg (Pararas-Carayannls, 1973).
Sewage sludge consists of ~5% solid material. When this material 1s
discharged from a barge, a portion of solids -sinks to the bottom while the
remainder 1s suspended 1n the water column for varying amounts of time. The
bottom temperature at the site ranges from 9.8-12.3°C In the summer (Reid
and O'Reilly, 1981). Previous Investigations of the New York Bight have
Included determinations of bacteria and protozoa pathogenic for both humans
and marine organisms. Thus, Acanthamoeba. a pathogenic protozoan, has been
Isolated from sediments In the vicinity of the dump site and from stations
between the site and the shoreline to the north. Pathogenic human
enterovlruses have been Isolated from the surface water, sediment and crabs
collected In this area (Table 2-1) (Goyal et al^. 1984a).
2-4 ' '
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TABLE 2-1
\ i -
Isolation of Human Enterovlruses from New York Bight Dump S1tea
Year Station No.b
1980 5
20
21
30
34
1981 4
7
9
14
19
25
39
62C
Depth
(m)
35
12
21
34
54
20
25
36
74
14
1
42
17
Virus Type
Unidentified
Echo 1
Unidentified
Echo 7
Echo 1
Coxsackle 83
Coxsackle 85
Echo 1
Echo 1
Coxsackle 83
Coxsackle 83
. Echo 1
Coxsackie 83
No. of Viral
Isolates/kg
of Sediment
18
64
60
182
56
108
12
30
4
84
14
2
d /
aData taken from Goya! et al., 1984a. Total number of samples examined
were: In 1980, 30 sediments and 8 crabs; 1981, 43 sediments and 13 crabs.
bStat1on numbers established by the Northeast Monitoring Program.
cCrab sample; all others are sediment samples.
^Positive by cytopathlc procedures and not by plaguing.
2-5
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Fecal conform bacteria have been Isolated from the bottom sediments of
the New York Bight 1n concentrations as high as 23,000/100 ma. of sediment
(Reid and O'Reilly, 1981). Fecal conforms have been Isolated from crabs
and lobsters that Inhabit the area. At one station, salmonellae were
Isolated from scallops. It 1s Interesting to note that fecal conforms were
not detected at. this station 1n either the animals or In the bottom
sediments (Reid and O'Reilly, 1981).
Members of the genus Thermoactlnomyces have an optimum growth tempera-
ture of 50°C and are unable to grow 1n cool waters. Al-D1wany and Cross
(1978) advocate their use as Indicators of mlcroblal contribution to fresh-
waters from terrestrial sources. Recently, Atwell and Colwell (1986) also
considered them to be useful markers to study the distribution and survival
of microorganisms 1n estuarlne and marine environments. Further studies are
necessary to determine 1f this 1s true.
The spores of a fecal Indicator, Clostr1d1um perfrlngens. have been used
to trace the movement of sewage materials from the area of the New York
Bight dump site. The highest spore densities found were not at the dump
site but 1n the Chrlstlaensen Basin to the Immediate west (Cabelll and
Pedersen, 1982). Spore densities 1n sediments extending from the Basin
toward the Long Island coast decreased exponentially with decreasing depth
to where the water 1s ~18 m deep. Thereafter, spore densities became
relatively constant, presumably because of settled sewage particles from
polluted waters emerging from embayments and ocean outfalls along the coast.
Host of the Indicators of sewage material were translocated to the southeast
along the course of the Hudson Shelf Valley; spore densities also decreased
exponentially with distance, but at a lower rate. Elevated spore densities
were detected to a distance of at least 105 km along the course of the Shelf
Valley.
2-6
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No evidence was found during the study that sewage sludge disposal at
the New York Bight dump site Increased the risk of swimming-associated dis-
ease at any New Jersey, New York City or Long Island beaches. Moreover, C.
perfrlngens spore densities 1n the water column or bottom sedljrjents
Indicated that dumped sewage sludge did not reach the shore 1n significant
quantities anywhere along the Bight (Cabein and Pedersen, 1982).
2.3.2. Philadelphia Dump Site. The Philadelphia sewage sludge dump site
1s a 172-km2 area located -70 km east of Ocean City, MD at roughly
28°23'N, 74°15'W. The site lies over the continental shelf 1n waters
40-60 m deep. Sewage sludge from the cities of Philadelphia, PA and Camden,
NJ was dumped at this site from 1973-1980. During 1973-1977, this site
received 2.5x10* kg of sludge (Table 2-2). The sludge components appeared
to collect on the ocean bottom, for the most part, 1n regions to the south-
east, south and southwest of the dump site, rather than primarily within the
boundaries of the site. The net water movement was In those directions.
Tidal and wind-Induced currents were apparently of sufficient strength to
sweep most released sludge outside the boundaries of the release site.
Rather than accumulating on the bottom In a uniform layer, the sludge-
derived materials collected in multiple, separate deposits in shallow topo-
graphic depressions running through the area.
Since 1973, -20 oceanographic cruises have been made to this area
before, during and after the dumping of sludge. The baseline characteriza-
tion of the area in 1973 indicated the site was clean and unpolluted.
Environmental changes have since appeared in the benthlc environment at and^
adjacent to the dump site. These changes have included accumulation of
metals and other toxic materials in organisms and sediment, changes in com-
munity structure, changes In abundance of different species, Increased rates
2-7
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TABLE 2-2
Quantity of Sludge Disposed at Philadelphia Dump Site*
Site Year
1973
1974
1975
1976
1977
1978
t
i
1979
1980
Quantity of Sludge
(kg x 106)
222
700
544
544
481
381
240
136
*Source: Reid and O'Reilly, 1981
2-8
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of mortality 1n the ocean quahog (Artlca Islandlca). and the appearance of
sludge, beds, sewage bacteria, pathogenic protozoa (Acanthamoeba) and dis-
ease 1n crabs {Sawyer et al., 1982).
0'Halley et al. (1982) compiled data on the recovery of fecal Indicator
bacteria and acanthamoebae from bottom sediments, which were collected from
the Philadelphia dump site on six different cruises from April 1978 through
August 1980. A total of 400 sediment samples were examined from stations
located between the 40 and 70 m Isobaths In a 6860 km2 area 1n and around
the disposal site. Total conforms, fecal conforms, fecal streptococci and
pathogenic amoebae were Isolated from 112 samples. Recoveries extended 37
km northeast and southwest of the dump site, but the highest percent of
positive stations was located <9 km from the center of the sludge release
site.
This site has also been monitored for the occurrence of human pathogenic
viruses In water, sediment and crabs since 1980. During 1980 and 1981,
several samples from a transect north to the New York Bight Apex were also
examined. During 1980 and 1981, 28 samples of water (sample size 380-760
a) and 104 samples of sediment (-300-500 g) were examined, of .which one
sample of water and 12 samples of sediment yielded viruses as shown In
Table 2-3.
Sludge dumping at this site ceased 1n December 1980. Goyal et al.
(1984a) Isolated viruses from sediment and crab samples In June 1982 (17
months after the cessation of sludge dumping). Their observations Indicate
that human pathogenic viruses can survive for at least 17 months 1n the
natural marine environment. Since the dump site 1s 64 km from the coast, 1t
1s reasonable to assume that these viruses originated from sludge barges and
not from any other source. The range of temperatures at different depths
2-9
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TABLE 2-3
Isolation of Viruses from Philadelphia Dump Site
and the Transect to the New York Bight3
Year
1980
1981
Stat1onb
No.
8
G 19
80—6
SH.45
KN 49
KN 49
E-12
205
80--6
.81-11
81-14
KN 46
KN 50
Depth
(m)
46
65
25
18
58
58
49
57
27
21
21
42
24
Virus Type
Echo 1
Unidentified
Coxsackie 63
Coxsackle B5
Coxsackie B5
Coxsackle 63
Pol 1o .2
Echo 9
Echo 1; Polio 2
Polio 2
Coxsackle B5
Echo 1
Echo 1
No. of Viral
Isolates/kg
of Sediment
20
46
50
15
12
2
12
8
22
30
8
56
4
aData taken from Goyal et al. (1984a). Total number of samples examined
were: 1980, 10 water and 42 sediments; 1981, 18 water and 62 sediments.
bThe numbering system was devised by EPA Region III.
2-10
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observed at the Philadelphia dump site during a cruise In 1983 1s shown 1n
Table 2-4.
2.3.3. The I06-H1le Deep Water Site. The 106-mile site was first used
for waste disposal 1n 1961. The U.S. EPA designated the 106-mile ocean
disposal site for sewage sludge disposal on a 5-year Interim basis 1n 1984
(COM, 1984).
From 1961-1978, -5.1 million metric tons of chemical wastes, 102,000
metric tons of sewage sludge and 287,000 metric tons of digester clean-out
sludges were disposed of at the 106-mile site (Schatzow, 1983). More than
100 industries have used the site for waste disposal.
A small amount of municipal sewage sludge has been disposed of at the
106-mile site. The City of Camden, NJ used the site during 1977 and 1978,
and digester clean-out sludges from New York/New Jersey metropolitan area
sewage treatment plants have been discharged there since 1974. However,
most of the ocean-disposed sewage sludge has been discharged at the 12-mile
site 1n the New York Bight Apex. As of March 1986, permittees currently
using nearshore sites may dispose of wastes at the 106-mile site. Such
relocation will result in a large increase in the amount of wastes
discharged at the site.
Currently, the DuPont plants dispose of -20,000 metric tons of acid-iron
waste and 180,000 metric tons of caustic waste per year, and the New York
area sewage authorities dispose of -35,000 metric tons of digester clean-out
(municipal) sludges. These activities are expected to continue. Now that
the 106-mile site has been designated for the receipt of municipal sludges,
1t is expected that -7 million metric tons of New York/New Jersey sewage
sludge currently being dumped at the 12-mile site will be discharged at the
106-mile site.
2-11
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TABLE 2-4
Temperature Ranges Observed 1n Relation to Depth at the
Philadelphia Sewage Sludge Dump Site (1983)a»b
Depth
(m)
Temperature (°C) Ranges Observed
at Various Stations (10 Stations)
Surface
5
10
15
20
25
30
35
40
45
55
14
16
15
11
7
6
6
6
6
6
6
.2
.4
.4
.1
.0
.8
.0
.0
.0
.4
.9
_
_
_
_
_
_
_
_
_
21
21
19
16
14
8.
7.
7.
7.
and
(1
»
.
•
»
»
7
2
3
1
7
9
4
8
5
3
.0 (2
readings)
reading)
aSource: O'Halley, 1983
bSal1n1ty range of 30-33 parts per thousand
2-12
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3. PATHOGENS OF CONCERN
Processed sewage wastes often contain residual pathogens, such as
viruses, bacteria, cysts of protozoa and ova of helminths. However, most
outbreaks of sewage-related disease have been attributed to the use of raw
sewage, raw sludge or night soil on food crops consumed raw, and to contami-
nation of drinking water from septic tanks or by consumption of raw, shell-
fish from sewage-polluted waters. The principal pathogens found in sewage
can be divided Into four groups: bacteria, protozoa, helminths and viruses.
Sewage treatment practices reduce the number of the above organisms, but
there 1s ample evidence to Indicate that effluents and sludges contain
detectable amounts of each of the above four groups. The amounts and
variety of pathogens present 1n sewage vary from community to community and
are dependent upon urbanization, season, population density, ratio of
children to adults and the sanitary habits of the community. Figure 3-1
presents the average number of waterborne-cMsease outbreaks from 1920-1980.
3.1. VIRUSES
More than 100 different virus types may be present 1n raw sewage (Table
3-1). The 11st of pathogenic human enteric viruses that could be present In
sewage has Increased by 14 during the last decade (Table 3-2). There are
obviously many more viruses yet unrecognized that could be present In
domestic wastes. Unfortunately, most of the knowledge on viruses In sewage
1s of those associated with gastroenteritis. Exceptions are certain entero-
vlruses that are associated with a wide variety of diseases and adeno-
vlruses that may cause eye Infections. Enteroviruses are often associated
with more serious Illnesses such as hepatitis, meningitis, myocarditis and
paralysis (see Table 3-1).
3-1
-------
3£
2
J3
XI
E
15
3
C
CD
I
so :YiYiTi~i~~~i~-~-~
20 iff
22
23
_-21
41
39
22
-zio:-:
12
11
14
25
39
FIGURE 3-1
Average Annual Number of Waterborne-Dlsease Outbreaks, 1920-1980
Source: Gerba and Goyal, 1985
3-2
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TABLE 3-1
Enteric Viruses That May Be Present 1n Sewage and Sludge*
Viruses
Type
Symptom and/or Disease Caused
Enterovlruses:
Pollovlrus
Echovlrus
Coxsack1ev1rus
Coxsacklevlrus
New enterovlruses
(Types 68-71)
Hepatitis Type A
(enterovlrus 72)
3
31
23
6
4
Meningitis, paralysis, fever
Meningitis, diarrhea, rash, fever,
respiratory disease
Meningitis, herpanglna, fever,
respiratory disease
Myocarditis, congenital heart
anomalies, pleurodynla, respiratory
disease, fever, rash, meningitis
Meningitis, encephalitis, acute
hemorrhaglc conjunct1v1t1es, fever,
respiratory disease
Infectious hepatitis
Norwalk virus
Cal1c1v1rus
Astrovlrus
Reovlrus
Rotavlrus
Adenovlrus
Pararotavlrus
Snow Mountain Agent
1
1
1
3
2
40
unknown
unknown
Diarrhea, vomiting, fever
Gastroenteritis
Gastroenteritis
Not clearly established
Diarrhea, vomiting
Respiratory disease, eye
Infections, gastroenteritis
Gastroenteritis
Gastroenteritis
*Source: Gerba and Goyal, 1985
3-3
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TABLE 3-2
Newly Recognized Viruses That Can Be Transmitted by Water3
Date Recognized as
New Agent
Virus
1972
1973
1975
1976
1977
1978
1979
1980
1981
1982
1983
Norwalk Agentb»c
Rotav1rusb
Astrovlrus
Cal1c1v1rus
Hawaii Agent
W-D1tch1ng Agent
Cockle Agentc
(enterovlrus)
Paramatta Agent
Otofuke Agent
-Adenovlrus 40
Adenovlrus 41
Marlon County Agent
Snow Mountain Agentb»c
Pararotavlrus
aSource: Gerba, 1984
bDocumented waterborne outbreaks
Documented foodborne outbreaks
3-4
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The most commonly 'Studied enteric viruses In sewage and sludge are the
enteroviruses, which Include poliovlruses, coxsackie A and B viruses, echo-
viruses, hepatitis A virus and other recently classified enterovirus types.
Several new presently unclassified enterovlruses, which have been respon-
sible for foodborne outbreaks in Australia, have recently been isolated In
cell culture (Grohmann, 1985). While many of the enterovlrus infections
such as those caused by poliovirus may be asymptomatic, symptomatic
infections may be as high as 95% during outbreaks of hepatitis (Lednar et
al., 1985). A great deal of Information is available on the removal of
enteroviruses by sewage treatment and many studies have been conducted on
their occurrence in sludges (Leong, 1983).
Rotaviruses are now recognized as a major cause of childhood gastro-
enteritis, sometimes resulting in dehydration and death in infants and
adults (Gerba et al., 1985). Several waterborne outbreaks have been docu-
mented .(Gerba et al., 1985) and-the virus has been isolated from sewage
sludges (Gerba, 1986).
The Norwalk virus has been demonstrated to be the cause of numerous
waterborne and foodborne outbreaks of epidemic gastroenteritis (Gerba,
1984). Since methods have not been developed for its isolation in cell
culture, its occurrence and concentration in sewage and sludges is unknown.
Astrovlruses, caliciviruses, cornaviruses, pararotaviruses and several other
Norwalk-like agents have been recognized as a cause of human gastro-
enteritis but little is known about them. Laboratory methods are currently
not available to study most of these agents and they await further char-
acterization.
Adenoviruses primarily cause respiratory and eye Infections although
several new types have been found associated with gastroenteritis (Gary et
al., 1979).
3-5
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3.2 BACTERIA
A number of bacterial pathogens may be present 1n sewage. These
Include, but are not limited to, Staphylococcus. Salmonella typhlmuMum.
Vibrio cholerae. Hycobacterlum. C1ostr1d1um perfringens. Campylobacter sp.,
Yers1n1a enterocol1t1ca. Leptosplra sp. and L1ster1a monocytogenes. The
bacteria most commonly found In sewage, and the diseases they cause, are
shown 1n Table 3-3. The pathogenic bacteria commonly enter a new host by
1ngest1on or by Inhalation. The major symptom caused by most of these
bacteria Is diarrhea but they may also cause generalized or localized
Infections (for example, typhoid and other enteric fevers caused by
salmonellae).
It should be pointed out that most of the bacteria mentioned 1n Table
3-3 are capable of producing a carrier state In Infected persons. Thus, In
communities where these Infections are endemic, a proportion of perfectly
healthy Individuals will be excreting pathogenic bacteria.
3.2.1. Salmonella. In the United States, Salmonella and Shlgella are two
enteric bacteria of concern. Salmonella species are responsible for >2
million cases of salmonellosls annually 1n the United States (Burge and
Harsh, 1978).
Salmonella consumption may cause Infection, and Infected persons can
become carriers, although a permanent carrier Is a rarity. Many carriers
are short-term convalescent or active cases. Infants, once Infected,
frequently become long-term carriers and cause familial outbreaks. Pets
such as turtles, reptiles, birds, cats and dogs also can be a source of the
pathogen. Even In developed countries, where water use 1s relatively high
and salmonellosls relatively rare, raw sewage may contain up to 104
salmonellae/a, (Feachem et al., 1983).
3-6
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TABLE 3-3
Bacteria and Parasites Pathogenic to Man that Hay Be Present
1n Sewage and Sludge*
Group
Pathogen
Disease/Symptom Caused
Bacteria Salmonella
Shigella (4 spp.)
Enteropathogenic
Escherichia coll
Yersinia enterocolitica
Campylobacter jejuni
Vibrio cholerae
Leptospira
Protozoa Entamoeba histolytica
Giardia lamblia
Balantidium coli
Cryptosporidium
Helminths Ascaris lumbricoides
(Roundworm)
Ancyclostoma duodenale
(Hookworm)
Necator americanus
(Hookworm)
Taenia saginata
(Tapeworm)
Trichurls
(Whipworm)
Toxocara
(Roundworm)
Strongyloides
(Threadworm)
Typhoid, paratyphoid, salmonellosis
Bacillary dysentery
Gastroenteritis
Gastroenteritis
Gastroenteritis
Cholera
Weil's disease
Amoebic dysentery, liver abscess,
colonic ulceration
Diarrhea, malabsorption
Mild diarrhea, colonic ulceration
Diarrhea
Ascariasis
Anemia
Anemia
Taeniasis
Abdominal pain, diarrhea
Fever, abdominal pa1n
Abdominal pain, nausea, diarrhea
*Source: Gerba and Goyal, 1985
3-7
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Salmonella species are a cause of diarrhea and, less commonly, enteric
fever throughout the world. With the exception of £. typhl and S. para-
typhl, Salmonella bacteria can Infect many species of mammals, birds,
reptiles and other animals. Waterborne outbreaks of salmonellosls have
chiefly been associated with S_. typhlmurlum and much less frequently with S.
paratyphl or other Salmonella serotypes (Feachem et al., 1983).
It 1s also reasonable to assume that sludges from sewage treatment works
will contain salmonellae. Reported concentrations vary greatly and may
change seasonally. In England the concentration of salmonellae/100 ma of
sludge has been reported to be 70 with 7% of samples containing >2400
(McCoy, 1979). In Switzerland >90% of raw sludge samples contained
Salmonella organisms ^at a concentration of 104-106 salmonellae/100 ma.
(Hess and Breer, 1975; Obrlst, 1979). In a review by P1ke (1981) the
geometric mean counts of salmonellae 1n raw sludge In different areas of
England and Wales varied between 8 and 1400/100 mi. Salmonellae were more
numerous and more frequently Isolated from sludge at treatment works serving
communities of 10,000-100,000 people than at works serving larger or smaller
communities. Flndlay (1973) and Jones et al. (1977) reported that
salmonellae can multiply vigorously 1n sterilized sludge or slurry, but
under natural conditions are strongly Inhibited by the activity of other
mlcroflora.
Salmonella species are found 1n a wide variety of nonhuman environments,
Including estuarlne and marine waters where there 1s fecal contamination
from domestic or agricultural wastewater discharges. Colwell and Kaper
(1978) reported that the ratios of salmonellae to. fecal conforms 1n
V
Chesapeake Bay ranged from 1:100-1:1000 and that there were <240
3-8
-------
salmonellae/100 ma. in Baltimore Harbor. In a previous study from that
same laboratory Carney et al. (1975) were unable to Isolate salmonellae in
an extensive survey of microbiological pollution In a subestuary of
Chesapeake Bay, despite occasionally elevated concentrations of up to <5400
fecal coliforms/100 mi. In a study of coastal canal communities in Texas,
Goyal et al. (1977, 1978) Isolated salmonellae from 47% of sediment samples
and from 3% of water samples. The concentration of salmonellae in sediment
was between 0 and 150/100 ms..
3.2.2. Shigella. Shigellosis or bacillary dysentery is an acute
diarrhea! disease caused by bacteria of the genus Shigella. Shigellosis has
a worldwide distribution with the highest incidence in communities where
hygiene 1s poor. These organisms are usually transmitted by the direct
fecal-oral route. Infected persons with diarrhea typically excrete
105-109 shigellae/g of wet feces, whereas symptomless carriers may
excrete 102-106/g (Dale and Hata, 1968). The incidence of Shigellosis
1n the United States reported to the Centers for Disease .Control in 1958
(Reller et al., 1969) was 4.6 cases/100,000 population and is increasing
steadily. The actual incidence 1s certainly very much higher, than the
reported Incidence, perhaps by a factor of 100. In the United States 38
waterborne outbreaks of shigellosls involving 5893 cases were reported from
1961-1975 (Black et al., 1978). An outbreak due to Shigella sonnei was
linked with bathing in a polluted section of the Mississippi River in Iowa
(Rosenberg et al., 1976). Sewage may contain between 10 and 104
shigellae/a,. It has been observed that survival in feces and sewage 1s
curtailed by the activity of the large populations of other bacteria
present. However, survival is enhanced at low temperatures.
3-9
-------
3.2.3. Fecal Indicator Bacteria. The fecal Indicator bacteria Include
the total conforms, the fecal conforms, EscheMchla coll. fecal
streptococci, Clostr1d1um perfrlngens. Pseudomonas aeruglnosa.
B1f1dobacter1um. Bacteroldes. and other bacteria that are excreted 1n large
numbers by healthy, warm-blooded animals and that are not normally enteric
pathogens.
Fecal Indicator bacteria are always present 1n high concentrations 1n
fresh sludge. Concentrations of 106-108 total conforms, 10S-1(P
fecal conforms and 104-106 fecal streptococd/g of sludge are normal.
Dudley et al. (1980) Investigated aeroblcally digested sludge and two
primary sludges 1n Texas and found 5xl05-5xl06 fecal conforms and
7xl04-5xl05 fecal streptococc1/g of suspended solids. Conforms In
sludge may survive for several months under cool, moist conditions. Growth
may also occur and this will be more rapid at warmer temperatures. Numerous
studies have documented high levels of Indicator bacteria (<103-105/100
ma) 1n ocean or estuaMne waters near sewage outfalls (Edmond et al.,
1978; Goya! et al., 1977, 1978, 1979a).
3.2.4. Escher1ch1a coll. In the last few years, 1t has become clear that
various forms of E_. coll are a major cause of diarrhea. The diarrhea pro-
duced by E_. coll cannot be differentiated clinically from similar diseases
produced by other enteric pathogens. These various pathogenic forms of E..
coll are enterotoxlgenlc, enterolnvaslve and enteropathogenlc. Enterotoxl-
genlc strains of E_. coll produce enterotoxln(s) and can cause a cholera-like
syndrome 1n Infants, children and adults. Enterolnvaslve strains produce
disease by Invading the colonlc mucosa, as do Shlgella strains. The
enteropathogenlc strains Include some enterotoxlgenlc and enterolnvaslve
strains besides a few other strains whose mechanism of action 1s not known.
3-10
-------
Sack et al. (1975) examined 18 water sources used by the Apache Indians
1n Arizona and found 200-300 collforms/100 mfc; out of 47 E. coll Isolates,
three strains (6%) were toxin producing. Freljl et al. (1979) tested rivers
and wellwater 1n Ethiopia and found enterotoxlgenlc E_. coll 1n 5596 andi 14%
of samples from the two respective sources.
3.2.5. Vibrio cholerae. Cholera 1s probably the best known and most
feared of the dlarrheal diseases. The family V1br1onaceae Includes several
human enteric pathogens of the genus Vibrio. Of greatest public health
Importance are the organisms that have been traditionally called Vibrio
cholerae or the cholera vibrio. Other potentially pathogenic vibrios that
are clearly not V. cholerae exist. V. parahemolvtlcus Is a halophlllc
marine organism responsible for numerous outbreaks and attacks of food
poisoning associated with seafood (Colwell, 1985). It has a marine rather
than an enteric reservoir.
Excretors of the cholera vibrio are rarely found In the United States.
Cholera Infections might be anticipated only among recent world travellers
1n whom the carrier state probably would never exceed 30 days (Felsenfeld,
1966). Carrier rates reported 1n India vary from -1.5-7% 1n the general
population and from 4.5-33.8% among close contacts of cases (Pal et al.,
1973). A carrier of cholera may excrete 106 v1br1os/g of feces, whereas a
patient with an acute attack of cholera may pass 1013 vibrios 1n a day.
There are numerous reports of Isolation of Vibrio species from rivers,
tanks, ponds and wells 1n communities where cholera cases or Infections are
known to be occurring. Recently, however, 1t has been found that cholera
can occur 1n water and wastewater at sites distant from any known human
Vibrio Infection.
3-11
-------
There are very few reports of V. cholerae 1n sewage. This 1s probably
because 1n most developing countries the section of the population that
experiences the highest attack rate of cholera produces no sewage because
the houses do not have flush toilets. During an epidemic of cholera In
Israel, Kott and Betzer (1972) reported that Jerusalem's sewage contained
between 10 and 104 V. cholerae/100 ma. In Bangladesh, Daniel and Lloyd
(1980) reported geometric mean concentrations of 2600 and 160 vibrios/100
mi of very strong sewage In two refugee camps.
3.2.6. Vibrio parahemolvticus. V. parahemolvticus 1s a gram-negative,
halophlUc bacterium that, unlike most enteric bacterial pathogens, derives
from the marine environment. The reported densities 1n water vary from
undetected to 10V100 ma, whereas 1n sediments 1t may be
-------
3.2.8. Yers1n1a. It 1s only 1n the last few years that Y. entero-
colUIca has been recognized as an etlologlcal agent of acute enteritis.
Although 1t was first Isolated In the United States 1n 1923, 1t was not
recognized as a human pathogen until the early 1960s. This organism? has
also been Isolated from domestic animals such as cattle, sheep, pigs, dogs,
chinchillas and geese. The fecal-oral route of transmission 1s the most
common, but respiratory transmission Is also possible. Foodborne and
waterborne outbreaks have also been reported. In one study a dose of
3.5xl09 organisms was required to produce an Infection 1n human volunteers
(Morris and Feeley, 1976). It has been suggested that under natural
conditions It 1s likely that considerably smaller doses will produce
Infection 1n a proportion of the population.
Little 1s known about the occurrence and survival of Yers1n1a 1n the
environment. The organism has been Isolated from a variety of environmental
samples, especially food and water, but the Isolated serotypes are often not
those especially associated with human disease. The organism has also been
Isolated from the marine environment (Pelxotto et al., 1979). Eden et al.
(1977) reported an outbreak of Yers1n1a-caused enteritis assoqlated with
wellwater at a ski resort 1n Montana. Y. enterocolUIca has been Isolated
from raw and anaeroblcally digested sludges (Metro, 1983).
3.2.9. Pleslomonas shlgelloldes. P. shlgelloldes Is a gram-negative,
oxIdase-posHlve rod and belongs to the family V1br1onaceae. It has been
known to cause human gastroenteritis for almost 40 years, but outbreaks were
not reported in the past because of Inadequacies of Isolation and Identifi-
cation methods. Although considered mainly an aquatic species, Pleslomonas
also appears 1n mammals, birds and reptiles. It 1s found most often 1n
3-13
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fresh surface waters, but there are some reports of Us presence In
seawater. In seawater, Pleslomonas can survive for up to <22-25 hours
(Zakharlev, 1971). Also, once released 1n seawater, It cannot be recovered
outside of a 100-m radius from the point of discharge. Many recent studies
have Implicated this organism 1n waterborne and oysterborne outbreaks of
gastroenteritis (Miller and Koburger, 1985).
3.2.10. Hycobacterlum. Water was not considered to be of much Importance
1n the transmission of atypical, anonymous, opportunist, tuberculold or
nontuberculous mycobacteMa until recently. It Is now realized that water
may be the vehicle by which these organisms Infect or colonize the human
body (Collins et al., 1984; Gruft et al., 1979). The organisms that have
been Isolated from water Include Mycobacterlum kansassl. M. xenopl. M.
avlum. Intracellular variant of M. avlum and M. scrofulaceum. The three
latter organisms are grouped together as MAIS (MycobacteMum av1um-1ntra-
cellulare-scrofulaceum). M. marlnum has been recovered from seawater,
swimming pools and aquaria. M. fortultum and M. chelonel. both of which may
be opportunistic pathogens, have also been Isolated from water.
MycobacteMa have also been found 1n sewage. Collins et al. (1984)
Isolated M. kansas11 and M. xenopl from this source. Heukeleklan and
Albanese (1956) Isolated M. tuberculosis from raw sewage of four tuberculo-
sis sanatoria but not from three municipalities. They found that trickling
filters and activation did not remove tubercle bacilli from sewage waters
but chemical coagulation with ferric chloride and slow sand filtration did
remove them. The sludges produced by primary and secondary processes con-
tained tubercle bacilli that were not destroyed by anaerobic digestion nor
by air drying of these sludges.
3-14
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Of a total of 791 samples of seawater taken off the coast of France, 176
contained mycobacteria (Vlalller and Vlalller, 1977). All of these organ-
Isms, except three, were MAIS organisms. The possible sources of contamina-
tion 1n open waters are son and, to a lesser extent, human and animal feces.
Tuffley and Holbeche (1980) reported that MAIS complex 1s most fre-
quently encountered in the sputum of patients with pulmonary mycobacterlosls
1n Australia. The Isolation of disease-associated serotypes from both soil
and house dust supports the concept of the environment being the natural
habitat of this species and the source of human Infection. A number of
authors have Isolated MAIS complex from a variety of water sources. It has
been suggested that this species may be able to survive 1n water for a pro-
longed time. Based on these observations, 1t has been suggested that water
may play a role In MAIS transmission. However, others feel that there 1s
still Uttle evidence to Incriminate water as a vector. Tuffley and
Holbeche (1980) reported the Isolation of mycobacteria from 67/205 rainwater
tanks In three areas of Queensland. They found that the humans who consumed
the contaminated tank water were free of symptoms but had not been medically
examined. It was suggested that mycobacteria adhering to dust particles
distributed by mechanical cultivation might be the source of contamination.
The role of birds 1n contamination of rainwater tanks with M. avlum should
also be realized.
3.2.11. Leptosplra. Leptosp1ros1s outbreaks have been linked to the
contamination of water by urine from humans, pets and livestock (Craun,
1974). Sixty-one Washington State teenagers were Infected after swimming In
an Irrigation canal. The swimming hole was 183 m downstream from a site
frequented by cattle shedding Leptospira. Serologlcal tests 1n a central
coastal region of the Caspian Sea showed that 47% of the humans and 40% of
the livestock carried Leptospira antibodies (Burge and Marsh, 1978).
3-15
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The genus Leptosplra 1s distinct from other fecal bacteria 1n that 1t 1s
not normally transmitted from person to person. It Infects rodents and
other animals and occasionally Infects a human who has come Into contact
with Infected animal urine. Sewer workers are exceptionally exposed to the
risk of leptosplrosls. Leptosplra bacteria can survive outside the body of
the host depending upon favorable conditions. A favorable environment 1s
one that 1s moist and relatively warm, shaded from the ultraviolet light of
the sun, not salty and at a neutral pH.
CabelH (1978) stated that leptosplrosls has been reported with
Increasing frequency 1n the United States over the past 5 decades and that
many cases are no longer related to occupational exposure, but to contact
with soil or water contaminated by urine. Swimming or wading 1n small ponds
or creeks recently used by cattle or receiving runoff from nearby pastures
1s a common setting for Infection. In 1975, 119 cases of leptosplrosls were
reported 1n the United States, and 36 of them were attributed to contact
with water containing cattle urine.
3.2.12. Aeromonas hydrophlla. A. hydrophlla causes a variety of systemic
and localized diseases 1n mammals, birds and fish. This organism produces
enterotoxlns and causes diarrhea 1n humans. It occurs widely 1n soil and
surface waters and has also been Isolated from drinking water, even after
chlorlnatlon (Burke et al., 1984). Exposure to water contaminated with
Aeromonas species may lead to certain Infections, especially In
1mmunocomprom1sed persons. In healthy subjects, 1t may cause dlarrheal
Illness.
Motile Aeromonas strains are ubiquitous 1n the environment and are
considered to be normal Inhabitants of the fish gut. They are also recog-
nized as fish pathogens, and some could be pathogenic for humans and other
mammals.
3-16
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Joseph et al. (1979) described the first Incidence of a primary Infec-
tion of soft tissue In a human caused by two species of Aeromonas (A. hydro-
phna and A. sobMa). These organisms were Isolated from the leg wound of a
diver conducting operations 1n polluted water. These authors later surveyed
the area and Isolated 193 strains of Aeromonas. of which 25-30% were cyto-
toxlc and 172 were A. hvdrophila.
A. hvdrophlla 1s found 1n sewage, In thermal effluents and In almost all
aquatic habitats except hypersallne and hyperthermal waters. Some feel that
the number of unreported cases of Aeromonas-caused Illness 1n humans Is
enormous because the genus causes a mild, self-limiting gastroenteritis
(Blamon and Hazen, 1983). Nevertheless, many cases of gastroenteritis and
wound infections In man have recently been reported. It has also been shown
that Aeromonas strains Isolated from drinking water and estuaries are
capable of toxin production and may therefore be possible enteric pathogens
in humans (Burke et al., 1984).
3.3. PROTOZOA
Of the intestinal protozoa that have been documented to cause disease in
humans, three can be considered as important pathogens. These are the
amoeba Entamoeba histolytica. the cause of amoebic dysentery; the flagellate
Giardia lamblia. which often causes severe diarrhea; and Crvptosporidium.
which causes mild to severe diarrhea. These protozoa are transmitted by the
ingestion of the cysts usually found in contaminated water or food. The
amoeba cysts can survive well at fairly low temperatures and in damp
conditions.
3.3.1. Entamoeba h1stolvt1ca. E_. histolvtica may produce a symptomless
infection or mild pyrexls and diarrhea (sometimes bloody), with or without
3-17
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abdominal pain. Some strains of £. hlstolytlca are more virulent than
others, and 1t has been estimated that >80% of Infected Individuals are
asymptomatic. In the United States, the carriage rate of Entamoeba species
1s estimated to be 3-4% overall, but may be closer to 40% among adult male
homosexuals (Jones, 1979; Schmerln et al., 1977). An asymptomatic
Individual may excrete up to l.SxlO7 amoebic cysts/day In the stool.
Although trophozoltes of Entamoeba are also excreted In feces, they die very
rapidly and are not considered responsible for transmission and hence are of
no environmental significance. The cysts, however, survive for a long time
In the environment and hence are of significance. At 20°C, they can survive
for 6 months In water (Feachem et al., 1983).
Even though the amoebic cysts are prevalent 1n high numbers 1n many
communities, there 1s very little Information on their occurrence 1n the
extra-Intestinal environment probably because 1t 1s difficult to detect them
1n water and other environmental samples. In some outbreaks of amoeblasls,
however, the role of sewage-contaminated water has been clearly estab-
lished (Wang and Dunlop, 1954).
3.3.2. Glardla lamblla. Since 1977, G. Iambi 1 a has been the most
frequently Identified agent associated with waterborne diseases In the
United States (Craun, 1979). It causes a mild, self-limiting Infection In
man and Is very rarely responsible for a serious Illness. This flagellated
protozoan 1s the most commonly Isolated of all pathogenic parasites In the
United States. The symptoms, 1f present, Include frequent diarrhea with
greasy, foul-smelling stools, usually without blood. Intrafam1l1al Infec-
tion 1s well recognized.
The prevalence of 61ard1a Infection 1n various communities ranges
between 1 and 20%, with children between 1 and 5 years old having the
3-18
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highest Infection rates. Infected persons may pass up to 900 million cysts
per day 1n stools. The probable concentration of 61ard1a cysts 1n sewage in
the United States has been estimated as 9xl03-2xl05/a (Oakubowski and
Erlcksen, 1979). In Chicago, Fox and Fitzgerald (1977) reported <530
6iard1a cysts/a, of raw sewage. They cautioned, however, about the
Inadequacy of tests for Glardla cysts 1n water and other samples and
observed that cysts may be missed altogether 1n concentrations <4000/i 1n
water and that cyst counts underestimate the actual content by as much as
99%.
3.3.3. Acanthamoeba. Small free-living amoebas belonging to the genus
Acanthamoeba are not classified as parasitic protozoa 1n the same sense that
Entamoeba hlstolytUa. an agent of human dysentery, Is recognized as a
strict parasite. However, 1n the late 1960s these amoebas were discovered
to be capable of killing humans and animals. The new term, amphlzolc, was
proposed to provide a label for organisms having the ability to survive free
1n the environment and to cause disease or death in susceptible hosts. All
members of the genus Acanthamoeba were considered to be inhabitants of
freshwater and soil until Sawyer (1980) reported their isolation from
contaminated bottom sediments at the New York Bight sewage disposal site.
This first isolate was found to kill experimentally infected mice. Further
work demonstrated that all known species of Acanthamoeba form highly
resistant cysts that may persist in sewage sludge after the Indicator
bacteria have lost their viability. This prompted Sawyer (1980) to advance
acanthamoebae as indicators of the spread and persistence of pathogenic
microorganisms in coastal and offshore waters.
The total number of recognized Acanthamoeba species is 27, six of them
pathogenic after internasal inoculation into mice. Eight of the 27 species
3-19
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have been Isolated from marine sediments. The Acanthamoeba genus belongs to
the family of Acanthamoebldae (Sawyer et al., 1982). The type species of
the genus was originally named Hartmannella castellanll but later was
transferred to Acanthamoeba. Bacteriological studies Indicate that there Is
a high correlation between the distribution of fecal bacteria and frequency
of amoeba found 1n contaminated sea bottoms (O'Malley et al., 1982).
Studies at the Philadelphia dump site show that amoebae persist In
sediment for as long as 2.5 years after cessation of sludge dumping.
Acanthamoeba species appear 1n environments that are rich 1n bacterial food
organisms both 1n surface waters of the ocean as well as 1n bottom
sediments. Davis et al. (1978) demonstrated a well-defined association
between bacterial numbers In surface mlcrolayers of the ocean and the
abundance of amoebae.
Environmental factors that Influence the distribution of acanthamoebae
In ocean sediments are just beginning to be understood. Excluding other
considerations, studies clearly demonstrate a correlation between
sewage-associated bacteria and the frequency of viable amoebae cultured from
polluted sediments. Although 1t remains to be determined 1f sewage sludge
contains amoebic cysts that are artificially Introduced Into the ocean, 1t
has been shown that both pathogenic and nonpathogenlc species are present In
municipal sewage treatment plants (Lawande et al., 1979). A similar
relationship was found by Brown (1980) between conform bacteria and
acanthamoebae 1n New Zealand. He recovered amoebae from soil and freshwater
with most of the Isolates coming from samples with high conform counts. De
Jonckheere (1981) .sampled water from factories with thermal discharges and
found that 25% of his Isolates from warm waters were pathogenic to mice.
Thus, water temperature and an abundance of bacterial food are now
3-20
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recognized as two factors that Influence ecological relationships between
acanthamoebae and the environment from which they may be recovered.
It is difficult to predict the impact of the presence of amphizoic
acanthamoebae in aquatic environments, particularly those associated with
sludge dump sites or other polluted environments, on human health. In
contrast to the fatal disease caused by Naeqleria fowleri associated with
swimming, poor health has been recognized as a predisposing factor for
Acanthamoeba infections in humans. Fatal and nonfatal cases caused by
acanthamoebae have been reported primarily in persons with deficient Immune
systems or who are on immunosuppressive drug therapy and in alcoholics or
disease-weakened persons (Martinez, 1980).
Martinez (1980) found that most human deaths involved persons with defi-
cient immune systems resulting from debilitating diseases such as diabetes,
Hodgkin's disease and alcoholism. The public health effects of pathogenic
Acanthamoeba on humans have only recently emerged.
Sawyer et al. (1982) conducted a study of Acanthamoeba species at the
Philadelphia offshore wastewater sludge disposal site. Between April 1978
and August 1980, these authors participated in nine different cruises to
this site and collected a total of 460 sediment samples from 325 different
stations,. Of 315 stations sampled for bacteria, 63 were positive for
coliforms and 36 were positive for fecal conforms. Fecal streptococci were
isolated from 8/100 stations, and amoebae from 28/147 (19%). One or more
species of Acanthamoeba were recovered from 40/229 (17%) sediment samples.
The distribution of conform bacteria and amoebae showed that only 2/28 (7%)
stations positive for amoebae were outside the area positive for bacteria.
3-21
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The results of the Sawyer et al. (1982) study provided the first compre-
hensive account of the distribution of acanthamoebae 1n bottom sediments of
the open ocean. They found six different species of Acanthamoeba from sedi-
ments of the open ocean, and they all seemed to be associated with the dis-
tribution of wastewater-assodated bacteria. This association, however,
probably depended more on the abundance of bacterial food than on the source
of origin of the bacteria. In an earlier study Sawyer (1980) showed that a
New York Bight wastewater disposal site with high bacterial numbers yielded
acanthamoebae from 25/36 sediment samples (69%), whereas only 2/94 samples
from the Gulf of Mexico yielded these amoebae. They further surmised that
Acanthamoeba species may be present In 1-2% of the sediment samples
collected from unlmpacted ocean bottoms, whereas <100% of the samples
collected from areas used for the long-term disposal of wastewater sludge
may be contaminated with acanthamoebae.
The public health Importance of pathogenic free-living amoebae 1n sedi-
ments and shellfish beds 1s unknown because reported cases of granulomatous
amoebic encephalitis 1n humans have not been associated with marine environ-
ments. Deaths from Acanthamoeba species have been reported from many parts
of the world, and efforts are being made to Improve clinical diagnostic
methods.
3.4. HELMINTHS
The two most Important helminths for humans are the hookworm (Ancyclo-
stoma) and the roundworm (AscaMs).
3.4.1. Ancvclostoma. With the possible exception of schlstosomlasis,
ancyclostomlasis 1s of the greatest worldwide public health Importance.
Ancyclostom1as1s may be caused by one of the two species of hookworms:
Necator amerlcanus or A. duodenale.
3-22
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Ancyclostomlasis Is frequently symptomless but when symptoms are
present, these Include anemia, weakness and debility. The most common route
of Infection 1s by penetration of skin, especially between the toes or on
the feet and ankles. However, the third-stage Ancyclostoma larvae can also
Infect humans by 1ngest1on. In the United States 1t has been estimated that
700,000 persons are Infected annually, and It 1s especially common 1n poor
rural areas of the Southeast (Warren, 1974).
In Nagpur, India, <254 hookworm eggs were detected/a of sewage
(Lakshminarayana and Abdulappa, 1969). In South Africa, Nupen and
DeVHHers (1975) were able to detect six eggs/2, of settled sewage. In
sludge, the number of hookworms 1s much more than 1n sewage effluent. Thus,
9.6x10" hookworm eggs were recorded/a of sludge 1n Sri Lanka (H1rsh,
1932). Thelss et al. (1978) examined sludges from California, Georgia,
Indiana, Kentucky, Montana, Ohio and Wisconsin and found hookworm eggs only
1n sludge from Frankfort, IN.
3.4.2. AscaMs lumbrlcoldes. The eggs of Ascarls worm are very per-
sistent In the environment and are difficult to eliminate by sewage treat-
ment processes. It 1s a helminthic Infection of the small Intestine by the
human roundworm, A_. lumbrlcoldes. About 85% of the Infections are
symptomless. It 1s one of the most prevalent human helminths worldwide.
Waterborne transmission 1s possible but 1s of very minor Importance.
Infection may, however, take place by the Inhalation of eggs stuck to
particles of wind-blown dust.
AscaMasIs is also common In developed countries. Thus, there are an
estimated 4xl06 people Infected in the United States, with the disease
being especially common in the Southeast (Warren, 1974). Sinnecker (1958)
conducted a study in Germany from 1954-1956 that showed the prevalence of
3-23
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Ascarls eggs was 3% among sewermen, 16% among sewage treatment plant
workers, 30% among sewage Irrigation workers and 8% among a controlled group.
In a study by Thelss et al. (1978), Ascarls eggs were recovered from 95%
of sludge samples collected from seven sites In the United States, and 1t
was the most frequently Identified parasitic helminth. Host sludges
contained <50 eggs/g but sludge from Los Angeles contained <100 eggs/g. In
another study, Wright et al. (1942) found Ascarls eggs 1n 36% of sludge
samples from 17 army camps 1n the southern United States.
3.4.3. TMchurls trlchlura. Tr1chur1as1s, an Infection occurring In
humans, 1s caused by the human whlpworm T. trlchlura. Trlchurlasls 1s a
helminthic Infection of the large Intestine and cecum. Host Infections 1n
adults are asymptomatic, but there may be slight abdominal pain and
diarrhea. TMchuMs eggs, like Ascarls eggs, tend to settle 1n primary and
secondary sedimentation tanks and are therefore concentrated 1n the sludge
from sewage treatment plants. The fate of Trlchurls eggs during sludge
storage, digestion or composting 1s believed to be similar to that for
Ascarls eggs, but they are probably eliminated somewhat earlier during these
processes (Feachem et al., 1983).
3.4.4. Taenla. T. saglnata and T. soil urn, the beef and pork tapeworms,
live In the Intestinal tract where they may cause abdominal pain, weight
loss and digestive disturbances. The Infection arises from eating
Incompletely cooked meat containing the larval stage of the tapeworm, rather
than from wastewater-contamlnated material. Humans serve as the definitive
host, harboring the adult worm. The eggs are passed 1n the feces, Ingested
by cattle and pigs (Intermediate hosts), hatch, and the larvae migrate Into
the tissues, where they develop to the cystlcercus stage. The hazard 1s
then principally to livestock grazing on sludge application sites. Taenla
eggs are concentrated In sewage sludge and may survive for prolonged periods
3-24
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after land disposal (Feachem et al., 1983). Taenla eggs may not be
completely destroyed by all sludge treatment processes {Feachem et al.,
1983).
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4. SECONDARY RISKS FROM MICROORGANISMS
In addition to the direct risks of disease transmission by disposing of
sludge containing human pathogens Into the marine environment, other risks
to human health may be associated with this practice. These Include risks
associated with the presence of drug-resistant plasmlds, genetically
engineered organisms, and stimulation of the growth of native marine organ-
Isms that may be pathogenic to man.
4.1. DRUG RESISTANCE AND PLASMID TRANSFER
In addition to pathogens 1n wastes of human and animal origin, concern
has been expressed 1n recent years over antibiotic-resistant Entero-
faacterlaceae bacteria, which have become widespread as a result of the
extensive clinical use of antibiotics and their incorporation Into animal
feeds. Resistance is carried by extra chromosomal elements (R-plasmids) and
is transferable between cells, not only of the same species or genus but
among genera as well. Numerous genera of bacteria, Including Pseudomonas,
Aeromonas. Vibrio, Hemophilus. Streptococcus and Enterobacteriaceae have
been found to carry R-plasmids.
The argument that the presence of a large number of conforms or fecal
conforms in the absence of bacterial pathogens 1s of no consequence because
these organisms are usually considered as harmless Indicators of water qual-
ity is not necessarily true 1f the bacteria in question possess transferable
drug resistance. Once these organisms enter the gastrointestinal tract of
humans, they may colonize the human gut themselves, transfer their
resistance to already colonized bacteria or transfer their R-factors to the
sensitive pathogens with which their host may become infected (Smith, 1971;
4-1
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Feary et al., 1972). The potential of R+ conforms to transfer their
resistance to pathogens has a significant bearing on the subsequent
treatment of the person harboring them. Also, the hazards are not limited
to drug resistance alone. It has been reported that R-factors may enhance
the Infectlvlty and virulence of pathogens such as S_. typhlmurlum and
Shlgella (Anders.on, 1968; Gangarosa et al., 1972; Thomas et al., 1972).
R-factors may also carry enteropathogenldty among £. coll. thus making the
bacteria harmful Instead of normally occurring commensals (Geldrelch,
1972a,b).
The public health significance of bacteria carrying transfer factors 1n
the environment Is not at all clear. There have been few Incidents 1n which
danger to human health has been proven, although the resistance of the
epidemic strain of S_. typhlmurlum 1n Mexico to chloramphenlcol mediated by
the resistance transfer factor Illustrates the potential problem that
transferable resistance may create. Thus, Walton (1971) has called for
continued surveillance so that potential hazards may be dealt with
rationally.
A number of workers have reported on the presence of drug-resistant
conform bacteria 1n surface waters, the principal source being raw and
treated hospital and municipal wastes (Smith, 1971). These bacteria have
also been Isolated from rivers and coastal bathing waters and from fresh-
water mussels 1n New Zealand (Cooke, 1976).
A significant number of bacteria resistant to antibiotics and heavy
metals have been found In sediments from the New York Bight dump site
(Kodltschek and Guyre, 1974; Tlmoney et al., 1978). Some of these Isolates
were shown to transfer antibiotic resistance to salmonellae 1n laboratory
experiments (Kodltschek and Guyre, 1974). In a subsequent study, Stewart
4-2
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and KodUschek (1980) demonstrated that plasmld transfer between bacteria
can occur not only In the laboratory but also under existing field condi-
tions. Recently, Goyal and Adams (1984) were able to recover drug-resistant
fecal Indicator bacteria from water and sediment samples obtained frtbra the
Philadelphia sewage sludge dump site. These bacteria were Isolated 30
months after the cessation of sludge dumping at this location.
4.2. STIMULATION OF NATIVE MARINE PATHOGENS
Baross and Llston (1970) found that marine vibrios were favored in
waters rich In organic matter such as those Impacted by sewage and overland
runoff. Watklns and CabelH (1985) Investigated the role of organic content
of water, 1n particular that derived from wastewater discharges, on the
density of V. parahemolytlcus 1n the Narragansett Bay, RI. They showed that
wastewater effluents had an enhancing effect on V. parahemolytlcus 1n this
estuary and that the effect was Indirect, probably mediated by
b1ost1mulat1on of the food chain and manifested at the level of the micro-
fauna. This was based on their observation of V. parahemolytlcus densities
that were highly correlated with net zooplankton levels rather than phyto-
plankton levels.
V. parahemolytlcus has caused numerous outbreaks of gastroenteritis from
consumption of marine foods (Colwell, 1985). In addition, 1t may also cause
wound and ear Infections as well as secondary septlcemla. V.
parahemolytlcus occurs predominantly 1n coastal and estuarlne regions. It
cannot compete successfully 1n the high salinity, low temperature, low
nutrient and high hydrostatic pressure environments of the deep ocean
(Colwell, 1984). Temperatures <10°C Inhibit or reduce the growth of V.
parahemolytlcus. but 1t may grow at 5°C under laboratory conditions after
very long periods of Incubation. It 1s not Isolated 1n winter season except
4-3
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In low numbers In sediment. V. parahemolytlcus 1s not associated with
domestic sewage contamination In the Chesapeake Bay, a result reaffirming
the autochthonous nature of this organism in the estuarlne environment
(Sayler et al., 1976).
V. parahemolytlcus 1s sensitive to both heat and cold (killed at 55°C 1n
10 minutes). When stored In baskets 1n hot weather, the low concentrations
of vibrios found 1n healthy blue crabs can quickly explode Into astronomi-
cally large populations.
Hood and Ness (1982) conducted studies on survival of vibrios In shell-
fish. They found that storage of oysters as shellstock resulted 1n growth
and survival of vibrios, whereas shucking and washing resulted 1n an overall
decline 1n vibrios. In shellstock, \/. cholerae levels Increased by 1 log at
2°C In 1 week, whereas V. parahemolytlcus Increased at 20°C. After 7 days
of storage, however, the levels of vibrios either remained statistically the
same as Initial levels (as with V. cholerae) or declined (V. para-
hemolytlcus).
4.3. OPPORTUNISTIC BACTERIA
A number of bacteria exist In nature that may not cause any disease 1n a
normal, healthy person but may produce serious disease 1n 1mmuno1og1cally
compromised hosts. Until recently, Aeromones hydrophlla and Pleslouronas
sh1gello1des were considered exclusively to be opportunistic bacteria (Burke
et al., 1984; ZakhaMev, 1971). It 1s now known that Aeromones species
Isolated from water may possess virulence factors such as enterotoxlns and
cytotoxlns and may be potential human pathogens. In patients without
Immunologlcal abnormality, Aeromones species have been Implicated 1n
dlarrheal disease. More serious disease 1s produced In patients who are
either Immunologlcally compromised or are suffering from chronic disease
(Joseph et al., 1979).
4-4
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4.4. GENETICALLY ENGINEERED OR6ANISHS
The recent emphasis on DNA recombination technology Indicates that more
and more genetically altered organisms will enter our environment. It Is
prudent, therefore, to be cognizant of this fact and determine 1f these
organisms pose any threat to human health. It Is also essential to under-
stand the molecular basis of virulence and pathogenidty and to develop new
measures for the control of these pathogens.
4-5
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5. EXPOSURE PATHWAYS
The fate of microblal enteric pathogens may take many potential routes
1n the marine environment. Based on the literature review, those shown 1n
Figure 5-1 appear possible. Both field and laboratory studies have demon-
strated that pathogen transport by these pathways occurs In the marine
environment. Field studies at both the New York Bight and Philadelphia dump
sites have shown that fecal indicator bacteria and viral pathogens occur in
the surface waters and accumulate in the sediments. These organisms appear
capable of existing for years in the, sediment material (Goyal, 1984). Crabs
in the area of the sludge disposal site have been shown to contain human
enteroviruses. The crabs may become contaminated by several routes includ-
ing intake of sediment material during feeding and ingestlon of contaminated
fish and shellfish. Shellfish, being filter feeders, tend to accumulate
bacteria and viruses, and concentrations of these microorganisms in shell-
fish can be expected to be many times higher than the surrounding water.
Consumption of viral-contaminated shellfish is a continuing cause of
outbreaks of disease in the United States (Richards, 1985). Fish may become
contaminated by the same mechanisms as crabs.
Once associated with a marine organism, inactivation of human enteric
pathogens will probably be reduced. It 1s possible that pathogens may be
passed through several species in the marine food chain. For example,
shellfish may accumulate viruses from the marine water and later excrete
them into their feces (Metcalf, 1976), which are then consumed by polycheate
worms. The polycheate worms are consumed by crabs which then may excrete
the pathogens into the sediment where sediment resuspenslon causes the
pathogens to again be taken up by shellfish. The dump sites are often
5-1
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Z- >
flj UJ
I
5-2
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closed to shellfish harvesting, so this problem is alleviated. Animals such
as crabs, however, are not sedentary and may move and be caught in "clean"
areas. If they are not cooked properly before consumption, they may present
a risk (Hejkal, 1982; Siege! et al., 1976).
Contact with pathogens may also result from bathing or diving in pol-
luted marine waters. It has been established that even swimming in only
marginally polluted waters can result in observable increases in gastro-
enteritis among bathers (Cabelli, 1980). Divers are also at increased risk
of ear infections when working in sewage-contaminated waters (Joseph et al.,
1979). Offshore dump sites are not used for swimming. However, any
activity that acts to resuspend sediment will aid 1n its transport away from
a disposal site. Currents, wind, storms, divers and dredging activity can
result in sediment resuspension.
Aerosols are generated during the disposal of the sludge and by wave
action or dredging activities. Baylor and Baylor (1980) found that when a
bacterial virus was added to ocean surf, it readily formed an aerosol, which
was detected in the air along the beach. Bacteria and viruses are
concentrated from the water during aerosol formation and can occur in
concentrations 50-1000 times greater in the overlying air than in the water
(Blanchard and Syzdek, 1970; Baylor and Baylor, 1980).
Data are not available on the generation and transport of aerosols from
the dump site, which makes it difficult to draw any conclusions about risks
associated with aerosols. It is prudent, however, to remark that marine
microorganisms have been known to be transported as far as 160 km from the
ocean by winds (Baylor and Baylor, 1980; Gruft et al., 1975).
5-3
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6. PERSISTENCE OF PATHOGENS IN THE MARINE ENVIRONMENT
The survival of fecal Indicator bacteria and viruses 1n marine waters
has received a great deal of attention. Numerous studies have been con-
ducted on the factors controlling the survival of these organisms. However,
less Information 1s available on the survival of specific bacterial
^
pathogens, protozoa and helminths.
Sunlight and temperature appear to be the dominant factors 1n .con-
trolling conform and fecal conform bacteria survival 1n marine waters.
Salinity also appears to play a role. Temperature 1s certainly critical to
viral survival; sunlight may also play a role, but Its Influence has not
been studied extensively. Once an enteric pathogen reaches the sediment,
Its survival appears to be greatly prolonged. Persistence 1n mollusks also
seems to be prolonged. Unfortunately, no previous studies have been
conducted on the survival of sludge-associated microorganisms 1n the marine
environment. Field studies at the Philadelphia dump site suggest that the
sludge accumulated 1n sediments may greatly prolong or cause the growth of
fecal Indicator bacteria.
It has been often found experimentally, and 1t 1s usually assumed, that
bacterial and viral survival 1n water follows an exponential curve; that Is,
the probabll-Hy of a bacterium dying 1n a given time Interval 1s dependent
on Us age. In other words, the reduction in bacterial concentration 1n
water follows a first-order equation of the form:
dt
-kC
(6-1)
6-1
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where
C = concentration of bacteria/volume of water (I.e., organisms/
100 ma) at time t
t » time (I.e., days)
k - first-order decay or die-off rate constant (expressed as l/t1me).
Although 1t 1s a good working equation, 1t has certain Inherent flaws.
For Instance, 1t does not take Into consideration the Injured bacteria or
the nonculturable but viable organisms. In a series of microcosm and field
studies 1t has been shown that V. cholerae and other pathogens can enter a
viable but nonculturable state (Colwell et al., 1985). It has also been
shown that these organisms continue to harbor the potential for virulence
because they contain virulent plasmlds and can produce fluid accumulation 1n
rabbit Heal loops (Colwell et al., 1985). Obviously, these bacteria will
not grow on common media and will be presumed to be dead.
Integrating Equation 6-1:
r r n-kt
C = C e
o
where
C0 « concentration of bacteria at t = 0.
Changing to base 10 and rearranging:
k =
If C - 0.1 C , then:
o
k =
logio
2.3
(6-2)
In much of the literature, death rates are expressed as k, In hourly or
dally units, rather than as tgQ values. The significance of t 1s that
1t 1s the time for reduction to a fraction of 1/10 of the starting population,
or a 1-log reduction. Since large changes 1n bacterial populations are best
handled 1n logarithmic terms, H Is of particular convenience. Times required
6-2
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for greater reductions may be readily calculated: tgg = 2xtgQ, tgg 9 =
3xt and so forth.
The following review summarizes the literature on persistence of enteric
pathogens 1n the marine environment.
6.1. MARINE WATER
6.1.1. Bacteria
6.1.1.1. INDICATOR BACTERIA — Numerous estimates of conform death
rates have been made In seawater. Chamber 11 n and Mitchell (1978) and
Mitchell and Chamberlln (1975) reviewed 87 of these estimates and concluded
that the tqn for conforms lay between 0.6-8 hours with a geometric mean
of ~2 hours. These values reveal considerably faster death rates of
conforms 1n seawater than 1n freshwater. The t__ values for freshwater
are between 20 and 115 hours with a median of ~60 hours. Death rates of
conforms 1n seawater are also considerably faster than the death rates
observed for viruses 1n seawater. For example, t for viruses was
estimated to be between 15 and 70 hours. There Is now general agreement
that fecal conforms are an Inadequate Index of saline water quality owing
to the greater persistence of enteric viruses 1n marine waters, especially
In shellfish-growing areas.
Many Investigators have tried to explain the rapid death of conforms 1n
seawater. Faust et al. (1975) found that the major determinants were
temperature, dissolved oxygen, salinity and protozoan predators. Recently,
an Increasingly convincing case has been built for the Importance of
light-Induced cell damage 1n determining conform death rates 1n seawater
(Chamberlln and Mitchell, 1978; Chojnowskl et al. 1979; Gameson and Gould,
1975). Experiments on fecal conforms 1n Sydney harbor, Australia showed a
minimum daytime t of 1.9 hours and a nighttime t of 40 hours for
6-3
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conforms (Bellalr et al.» 1977). According to Chamberlln and HHchell
(1978), fecal streptococci appear to be substantially less sensitive to
light-Induced 1nact1vat1on than conforms.
Temperature Is also an Important factor determining the rate of survival
of conforms. Even relatively small temperature differences can substan-
tially affect the death rate. Therefore, conforms discharged Into tropical
seawater may decline 1n numbers more rapidly than 1n temperate climates.
Jamleson et al. (1976) reported that In sterilized saline water a pathogenic
serbtype of E_. coll had a t of -40 hours at 4°C and ~8 hours at 37°C.
Vasconcelos and Swartz (1976) reported that E_. coll concentrations 1n
seawater declined by <2 log units at 8.9°C, but by 7 log units at 14.5°C
after 6 days. Burdyl and Post (1979) estimated a t -for E. coll of -110
yu ~
hours at 9°C and -21 hours at 19°C. Faust et al. (1975) reported a t5Q
for E_. coll 1n estuarlne water of 39 hours at 0°C and 14 hours at 30°C,
while Hancinl (1978) reported a tg_ of 60 hours at 0°C and 7 hours at 30°C.
Studies on the survival of conform and streptococci 1n sewage reveal
that survival Is greatly prolonged at cool temperatures when dissolved
oxygen 1s low (Hanes et al., 1964) or when the overall mlcroflora have been
reduced by chlorlnatlon or some other means. In warm climates with sewage
temperatures ~25-30°C, a >99X reduction 1n Indicator bacteria concentration
may be expected 1n -10-15 days, depending on the level of oxygenatlon of the
sewage.
Roper and Marshall (1978) found that mlcroblal parasites and predators
Increased 1n number directly as a result of the Introduction of £. coll 1n
natural seawater. After rapidly destroying these alien conforms, the
parasites and predators were reduced In numbers because of nonavailability
of suitable host organisms and because of predatlon by larger protozoa. In
6-4
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In seawater, near a sewage outfall, the parasites and predators were
enriched by the constant availability of host bacteria; the numbers of £.
coll. therefore, declined rapidly near the outfall. The rate of decline of
£. coll was slower in seawater samples taken further from the outlet.
Fecal streptococci survive longer in marine environments than fecal
conforms (Baross et al., 1975; PetrTlli et al., 1979). The tgo for fecal
conforms was 3.7 hours whereas for fecal streptococci it was 5.7 hours
(Pichot and Barbette, 1978). Baross et al. (1975) conducted a study on the
survival of pure cultures of E.. coli. S. fecalls. C. perfringens and V.
parahemolyticus under simulated deep sea conditions of low temperatures
(4°C) and hydrostatic pressure ranging from 1-1000 ATM over a 300-hour
period. Both E.. coli and S. .-fecalls survived at 250 and 500 ATM for a
longer time than at 1 ATM at 4°C. In addition, S. fecal is was quite
insensitive to 1000 ATM, whereas E. coli died at 1000 ATM within 50 hours.
In contrast, V. parahemolyticus and C. perfringens were quite sensitive to
pressure exceeding 250 ATM, and with both of these species there was a total
loss of viability of ~108 cells/ma within 100 hours at 1000 ATM and
within 200 hours at 500 ATM. In addition, the total numbers of aerobic
bacteria in sewage samples stabilized at 500 and 1000 ATM after 100 hours,
and at 1 and 250 ATM there was significant growth of sewage-associated
bacteria, which apparently utilized the organic compounds present in the
sewage samples.
Mancini (1978) reviewed the literature on conform die-off in the marine
environment and felt that it could be expressed as follows:
(t-20) K H
K = [0.8 + 0.006 (% seawater)] x 1.07 +. I K H [1 - e e ] (6-3)
t A e
where
6-5
-------
Kt - mortality rate/day
t = temperature (°C)
I. « average dally surface solar radiation (langleys/hr)
Ke s Ught extinction coefficient (length"1)
H » completely mixed depth of water (length).
Mandnl (1978) cautioned that the equation should only be used as a guide
for Initial estimates of conform mortality rates since the variation of
reported conform die-off 1n similar conditions Is quite large.
6.1.1.2. SALMONELLA — In raw sewage the tgo for S. typhlmuMum has
been reported to be 77-108 hours at 7-20°C (Green and Beard, 1938). It Is
reasonable to assume that Salmonella survival 1n sewage Is similar to that
of fecal conforms with a tgo of 20-100 hours In warm climates.
According to Petr1ll1 et al. (1979), salmonellae are more persistent In
marine environments than Is £. coll. They, therefore, considered £. coll a
poor Indicator of Salmonella and enterovlrus survival 1n marine
environments. In a laboratory study, Jamleson et al. (1976) added S,
typh1mur1um to samples of sterilized seawater adjusted to salinities of 0.5,
2 and 3.5% and stored them at 4, 25 and 37°C. They found that survival was
Inversely proportional to salinity and temperature. Maximum survival was
for 7 days at 4°C and 0.5% salinity and minimum survival was for 5 days at
37°C and 3.5% salinity. Survival of E_. coll was shorter than that of £.
typh1mur1um at all temperatures and salinities. Vasconcelos and Swartz
(1976) compared the survival of £. heldelberg and £. coll In sterilized
seawater at 14.5°C. The E.. coll concentration had declined by 6-log units
1n 6 days whereas S. heldelberg was reduced by only 1.5-log units 1n 6
days. Nabbut and Kuraylyyah (1972) Investigated the bactericidal activity
of seawater against S. typhlmurlum and found that autoclavlng and filtering
of seawater resulted In a loss of bacterlqldal activity. This Indicated
6-6
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that predators and competitors contribute significantly to bactericidal
activity of seawater. Other factors Include pH, salinity, toxic Ions,
temperature, sunlight and nutrients.
6.1.1.3. SHIGELLA — In surface waters contaminated by human^ feces
the concentration of Shlgella bacteria 1s low. Unlike salmonellae, E.. coll
and fecal streptococci, Shlgella species are excreted only by man. Survival
1n water depends upon factors such as the concentration of other bacteria,
nutrients, oxygen and temperature.
Survival Is most prolonged 1n very clean waters such as unchlorlnated
tap water or 1n polluted water containing nutrients but having a minimum of
other bacteria present; 1n these latter conditions shigellae may even grow.
Thus, Shlgella flexneM survived for <21 days 1n clean riverwater, for 47
days 1n autoclaved riverwater, for 9 days In wellwater, for 44 days 1n
autoclaved tap water and for 6 days 1n polluted wellwater at 19-24°C
(Talayeva, 1960). In sterilized water at 11-28°C Shlgella dysenterlae was
reported to survive for <93 days (McGarry and Stalnforth, 1978). It Is
Interesting to note that shigellae can grow 1n sewage-contaminated water;
thus, Hendricks (1971, 1972) reported that Shigella flexneri multiplied 1n
sterilized riverwater collected downstream from a sewage outfall. Growth
occurred at 30°C, but not at 20 or 5°C. No growth at any temperature was
recorded 1n water collected upstream from the sewage outfall.
There have been limited studies on the survival of shigellae 1n sea-
water. Nakamura et al. (1964) suggested survival times of 15-70 days at
15°C in seawater, which may be somewhat longer than those in freshwater.
This is In contrast to the fecal Indicator bacteria that die more rapidly in
seawater than in freshwater. According to Jamleson et al. (1976), how-
ever, Shigella dysenteriae survived for <6 days at 0.5, 2.5 and 3.5%
salinities even at 4°C.
6-7
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6.1.1.4. VIBRIO CHOLERAE — Studies on the survival of V. cholerae 1n
sewage suggest that In some wastewaters survival times of 1-24 days at
20-30°C can be expected. Survival times are shorter at warmer temperatures
and linger 1n sterilized sewage than 1n raw sewage. These rates may be
compared with typical tgQ values for conforms of 20-115 hours (median 60
hours) In surface waters and with 0.6-8 hours (mean 2 hours) 1n seawater.
The tg0 values for V. cholerae are not substantially less than those
reported for conforms and may be similar to those reported for other
'•r- : •
bacterial enteric pathogens. McFeters et al. (1974) made a direct
comparison of various bacteria In sterile wellwater and found the following
tcn values: Shlgella. 22-27 hours; conforms, 17 hours; Salmonella. 2-19
ou
hours; and V. cholerae. 7 hours. It has been suggested that V. cholerae
survives 2-5 times longer than £. coll. Pseudomonas and Aerobacter when they
are added to artificial wellwater and stored at 25°C (Pandit et al., 1967).
V_. cholerae 1s capable of multiplication and prolonged survival In some
wastewater (Daniel and Lloyd, 1980). The multiplication of V. cholerae 1n a
septic tank In Japan has been reported (MMWR, 1979). Multiplication of V.
cholerae 1n a trickling filter In Bangladesh has also been observed (.Daniel
and Lloyd, 1980).
In seawater V.. cholerae survives 2 months at 4°C and 6-60 days at
20-30°C. It 1s clear that survival can be greatly prolonged 1n
nutrient-rich waters and 1n seawaters that have been boiled or autoclaved
prior to contamination with Vibrio bacteria, thus eliminating competing
microorganisms and possibly also making the chemical composition of the
water more favorable for survival of V. cholerae. The survival of the genus
Vibrio 1s known to be curtailed considerably by sunlight.
6-8
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6.1.1.5. LEPTOSPIRA — The survival of Leptosplra species 1n water 1s
heavily dependent on the temperature and the level of bacterial
contamination. Thus, In rlverwater leptosplres survived for 8-9 days at
5°C, but for 5-6 days at 20-27°C. At 31°C their life span was reduced to
3-4 days (Chang ^et a!., 1948). Survival 1n water was greatly reduced by
high or low pH and by salinity, and they survived only for 18-20 hours In
seawater. The work of Jamleson et al. (1976) also confirmed that Leptosplra
species do not survive In saline water for a long time. At 0.5, 2.0 and
3.5% salinity, they survived for <24 hours at 4, 25 and 37°C, respectively.
In summary, Leptosplra microorganisms 1n clean sterile water at a cool
temperature may survive for <20 days, and they may grow and survive for 100
days 1n the presence of suitable nutrients. However, 1n water with a rich
bacterial flora and at warm temperatures, survival times are probably
between 1 and 5 days.
6.1.1.6. YERSINIA—Y. entercolltlca may survive for considerable
periods of time 1n cool, clean waters with a minimum of bacterial
competition (H1ghsm1th et al., 1977). By contrast, In sterilized saline
waters with 0.5, 2 and 3.5% salinities at 4, 25 and 37°C, respectively, an
Initial Inoculum of 1.5xl07 Yerslnla organisms/ma failed to survive for
>4 days, with a 6-Tog reduction after only 1 day (Jamleson et al., 1976).
6.1.1.7. CAHPYLOBACTER JEJUNI — Information Is not presently avail-
able on the survival of campylobacters In seawater. In one study, Blaser et
al. (1980) found that In autoclaved streamwater, a 7-log reduction took 5-33
days at 4°C, whereas 1t took 2-4 days at 25°C.
6.1.1.8. ANTIBIOTIC-RESISTANT BACTERIA — R+ bacteria may survive
longer or as long as antibiotic-sensitive bacteria 1n certain water
environments (Smith et al., 1974). Conforms with R-factors were shown to
6-9
-------
Increase 1n maturation ponds from 0.86 to 2.4% during treatment of
conventionally purified sewage (Grabow et al., 1973). R+ fecal conforms
are not cured In seawater nor do they have a detectably different survival
rate 1n sewage-contaminated seawater compared to drug-sensitive fecal
conforms (Smith, 1971). In a limited laboratory study, R+ bacteria were
found to survive as long as the antibiotic-sensitive ones In seawater
containing sediment material.
6.1.2. Enteric Viruses. The occurrence of enterovlruses 1n polluted
marine waters, Including areas receiving sewage sludges, has been
demonstrated In numerous studies (Kapuscinski and Mitchell, 1980, 1981;
Jones, 1981; Goyal, 1984). Viruses have been detected away from the
original source of pollution and In the absence of bacterial Indicators
(Goya! et al., 1979a; Lucena et al., 1982; Goyal, 1983). Many studies have
found that viruses persist far longer 1n marine water than Indicator
bacteria (Kapuscinski and Mitchell, 1980; Hugues et al., 1981; Lucena et
al., 1982). Enteric viruses have been reported to survive 2-130 days In
seawater In laboratory studies (Melnlck and Gerba, 1980).
Data from laboratory and field studies on survival of viruses In marine
waters have been reviewed (Akin et al., 1975; Kapuscinski and Mitchell,
1980). A number of variables have been found to affect virus survival,
Including temperature, salinity, mlcroblal antagonism, solar radiation and
association of viruses with solids. Of the many factors that can Influence
virus survival, temperature 1s perhaps the most Important. Hejkal and Gerba
(1982) compiled data from published studies on 1nact1vat1on of viruses 1n
seawater and analyzed them to determine If a predictive relationship existed
between Inactlvatlon rate and temperature. Based on 143 cases from the
published literature, the rate of Inactlvatlon varied with temperature
6-10
-------
according to the following equation:
Inactivatlon (log /day) = -0.184 + 0.0335 (temperature 1n °C). (6-4)
Laboratory studies have been limited to a temperature range of 10-37°C
and the observed relationship has been considered valid for onlyf these
ranges In temperature. The relationship Indicates that for each 10°C rise
1n temperature the 1nact1vat1on rate 1s approximately doubled.
A similar analysis was done using salinity as the Independent variable.
However, based on the published literature, no significant correlation was
found between viral 1nact1vat1on and salinity. While other factors may
Influence virus survival, they are still 111 defined and cannot be easily
quantltated. Thus, Lo et al. (1976) found that temperature rather than
salinity was the critical factor affecting the survival of pollovlrus type
1, echovlrus type 6 and coxsacklevlrus type B-5. In laboratory studies, all
three viruses were found to be stable at 4°C with Infectious virus still
detectable after 46 weeks of Incubation. In situ studies Indicated that
although the viruses were more labile 1n estuarlne and marine waters, they
still persisted for several months, especially during winter.
Almost all studies on virus survival in marine waters have been on
enteroviruses and collphages. One laboratory study suggests that simian
rotavlrus survival In marine waters is similar to that observed for
enteroviruses (Hurst and Gerba, 1980). No information on the survival of
hepatitis A virus In seawater 1s available. However, recent studies on its
survival in groundwater suggest that it can be expected to survive longer
than pollovlrus (Sobsey, 1985).
No studies have been conducted on the survival of sludge-associated
viruses 1n the marine environment. Such an association could act to greatly
prolong virus survival.
6-11
-------
6.1.3. Protozoa. The survival of amoeba cysts 1n water 1s primarily
i
dependent upon temperature. In seawater the salt concentration of seawater
does not affect Entamoeba hlstolytlca cysts and their survival may be as
high as 1n freshwater (Dobell, 1928; Khelssln and DmltMeva, 1935). At 25°C
E.. h1stolyt1ca may survive for 7-20 days. At 5°C, however, It may survive
>1 month (Kott and Kott, 1970).
Kott and Kott (1970) conducted a study to determine the survival of E_,
hlstolvtlca cysts by Inoculating cysts Into beakers containing seawater.
After Incubation times of 24, 48 and 72 hours at 20°C, the cysts were
removed by a flotation technique and tested for viability. It was
determined that £. hlstolytlca cysts Isolated from raw sewage survived In
seawater for 2 days but did not survive 3 days.
Sewage treatment may remove between 52 and 93% of 61ard1a cysts
(Panlcker and Kr1shnamoorth1, 1978). Aerobic digestion of sludge also kills
cysts (Fox and Fitzgerald, 1979). In unchloMnated tap water at pH 6.8, the
G1ard1a cysts survived for 6, 25 and 77 days at 37, 21 and 8°C, respec-
tively (Jarroll et al., 1980). No Information on the survival of Glardla
cysts In seawater could be located. However, their survival would appear to
be no greater than E_. hlstolytlca 1n this environment.
6.1.4. Helminths. Ascarls eggs can survive 1n a variety of environmental
conditions for periods of months or even years. They need small quantities
of oxygen to develop but can remain viable for long periods under anaerobic
conditions. In laboratory experiments It has been found that 97% of eggs
are killed after 2 days 1n seawater. They are considerably more resistant
than Trlchurls. hookworm or Entroblus eggs, but somewhat less resistant than
Taenla eggs (Livingstone, 1978). The specific gravity of Ascarls eggs 1s
~1.11, so they will settle 1n seawater with specific gravities of 1.0-1.03.
6-12
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Hookworm eggs can survive 1n sludge at 27°C for <43 days (Hirsh, 1932),
but In seawater their survival Is <5 hours compared with >30 hours for
Ascarls eggs (Livingstone, 1978). They tend to settle 1n water and
eventually accumulate 1n the bottom sediments.
6.2. SEDIMENTS-
6.2.1. Bacteria. More than 80% of the fecal Indicator bacteria In
estuary water have been found to be directly associated with suspended
sediments. Association of these fecal bacteria with sediment prolongs their
survival 1n the aquatic environment. Thus, transport through association
with suspended sediments may be a significant mechanism operating 1n the
aquatic environment. Mitchell and Chamberlln (1975) suggested that In
determining survival of pathogens 1n water, many people have equated
sedimentation with the removal or disappearance of bacteria, which Is not
correct. The effect of shallow versus deep waters and rivers vs. bays vs.
open ocean on bacterial survival 1s also not known.
RHtenberg et al. (1958) studied the distribution of conform bacteria
In sediments around three marine sewage outfalls In California and demon-
strated that conforms could be carried 1n the water for long distances away
from a sewage outfall, but never more than 1n sediments. Thus, at 1800 m
from the outfall boll, MPN of conforms was found to be <10/ma of water,
whereas sediments as far as 4.8 km from the outfall had conform populations
measurable 1n thousands and even tens of thousands/ cm2 of surface
bottom. The build-up of larger populations of bacteria in sediments was
ascribed to their longer survival time 1n sediments, but no proof was
presented. They further concluded that "sedimentation" was a major factor
1n the disappearance of conforms discharged into ocean waters.
An increasing body of evidence indicates that conform organisms are
capable of limited growth in polluted streamwater (Hendricks, 1972;
6-13
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Hendrlcks and Morrison, 1967). HendMcks and Morrison (1967) found that at
<15°C, an extract of river-bottom sediment provided a better nutrient source
for enterobacterla (Including Indicators and pathogens) than did Mverwater
from sites above and below a sewage treatment plant. They argued that
material loosely bound to bottom sediments was probably available for
mlcroblal use. In a later study, Hendrlcks (1971) washed river-bottom
sediments free of loosely associated chemical nutrients and eluted the
washed sediments with 0.3 M sodium phosphate buffer. It was shown 1n
respiration experiments that selected strains of EnterobacteMaceae were
able to metabolize this substrate. Subsequently, Gerba and McLeod (1976)
demonstrated Increased survival and limited growth of £. coli In a marine
system containing bottom sediments.
Several studies Indicate that on a volume basis greater numbers of
conforms and bacterial pathogens occur 1n bottom sediments than 1n
overlying water (Table 6-1). Hendricks (1971) found -90% of Salmonella
Isolates 1n sediments and demonstrated a higher recovery rate from river
sediments than from water. Similarly, Van Donsel and Geldreich (1971)
Isolated salmonellae from 22/48 bottom sediment samples, whereas only 4/48
water samples were positive for this organism. This study was performed 1n
freshwater systems Including bathing beaches, recreational lakes, and clean
and polluted rivers and creeks. The density of fecal conforms was also
found to be 100-1000 times higher in mud than in water. In several field
studies, a larger population of indicator bacteria and pathogens In
estuarlne sediments than in overlying waters has been found. Bablnchak et
al. (1977) examined 114 sediment samples from sewage sludge disposal sites
1n New York Bight and found the MPN of fecal conforms to be between 0 and
542,000/100 ma. When sediment samples were stored at 4°C for 4 days, no
appreciable change was detected in fecal conform counts; they concluded
6-14
-------
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that jm s_1.tu fecal conforms might persist longer, particularly when
sediment temperature Is low. Van Donsel and Geldreich (1971) also showed
that both fecal conforms and Salmonella species survived for 4 days when
mud was stored at 20°C.
Conform bacteria have been detected 1n the areas of sludge disposal at
both the Philadelphia and New York Bight dump sites (Goyal, 1984). Analysis
of sediments 1n the summer of 1985 at the Philadelphia sludge dump site
showed that conform bacteria were still present 4 years after sludge had
last been dumped at the site (Goyal, 1986). Fecal indicator bacteria
possessing multiple drug resistance were found 30 months after the cessation
of sludge dumping. '
6.2.2. Viruses. ;Numerous studies have documented the occurrence of
enterovlruses and rotaviruses in marine sediments (DeFlora et al., 1975;
LaBelle et al., 1980; Rao et al., 1984; Rao, 1985). Laboratory studies have
clearly demonstrated that virus adsorption to sediments prolongs their
survival time in marine waters (Gerba and Schalberger, 1975; Rao et al.,
1984). Although the observed protection against inactivation may be due to
a number of factors, thermostabiUzatlon of the virus appears to be the most
important (Liew and Gerba, 1980). The degree of protection is variable,
depending on the type of virus and the conditions of the experiment.
Generally when sediment 1s present, Inactivation rates of viruses in
seawater-molstened sand tend to be 4.5-fold slower than that in seawater
alone. Rao et al. (1984) found the Inactivation of poMovlrus type 1 and
rotavlrus SA-11 to be 2-2.5 times less in sediment than that observed 1n
estuarine water at 25°C.
Goyal et al. (1984a) Isolated enterovlruses from sediments from the
Philadelphia sewage sludge dump site 17 months after the cessation of sludge
dumping, but not 2 and 3 years after cessation (Goyal, 1986).
6-17
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6.3. FISH AND SHELLFISH
F1sh, shellfish and crabs that live 1n water contaminated by sewage
discharges are frequently found to contain enteric bacteria and viruses. In
addition,, 1t has been demonstrated In laboratory studies that lobsters,
sandworms, detrltal feeding fish, conch and aplysla can accumulate enteric
viruses (Siege! et al., 1976; Gerba and Goyal, 1978; Hetcalf, 1976). These
studies have demonstrated that human enteric pathogens can contaminate
seafood and be transmitted to man.
6.3.1. Bacteria
6.3.1.1. INDICATOR BACTERIA — Several studies have shown that
fecal Indicator bacteria are not part of the normal flora of the Intestines
of freshwater or saltwater fish (Geldrelch and Clarke, 1966; Feachem et al.,
1983). F1sh Intestines may contain fecal conforms and fecal streptococci
only when the fish have been living In fecally contaminated water, and these
bacteria may survive, and perhaps multiply, for periods of <14 days In fish
Intestines (Glantz and Krantz, 1965).
Geldrelch and Clarke (1966) studied the survival of various enteric
bacteria In the sterilized Intestinal contents of fish. In Intestinal
contents of carp at 10°C, salmonellae, shlgellae and fecal conforms
declined, whereas fecal streptococci grew slowly. At 20°C fecal strep-
tococci grew rapidly, fecal conforms and most salmonellae grew slowly, but
i. typhlmurlum and Shlgella declined. Jenssen (1970) found that a variety
of fish caught as far as 2.4 km downstream of a sewage outfall contained
Salmonella bacteria. Channel catfish, when experimentally Incubated,
continued to excrete Salmonella Into the water of holding tanks for 29 days.
Host Investigations of marine foods have centered on the bacterial
contamination of shellfish rather than fish. This Is because the method of
6-18
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filter feeding by bivalve mollusks concentrates bacteria In the same way It
concentrates viruses (Hetcalf 1978; Wood, 1979) and because mollusks are
often eaten raw or only lightly cooked. Goyal et al. (1979a) Investigated
oyster beds In Galveston Bay, TX and found fecal conform concentrations/100
mi of <2400, 46,000 and 46,000, respectively, In water, sediment and
oysters. Similar results were obtained by Slanetz et al. (1968). Hunger et
al. (1979) recorded that fecal conform concentrations In clams In the
Seattle area were <59 times higher than 1n the surrounding water.
Mitchell et al. (1966) studied the uptake and elimination of E_. coll by
the eastern oyster (Crassostrea vlrglnlca) 1n sterilized seawater at 20°C.
When the seawater contained -103 E.. col1/msu the oysters accumulated over
100/g within 4 hours. In similar experiments Hoff and Becker (1969)
reported that Olympla oysters (Ostrea luMda). In sterilized seawater con-
taining 10 £. col 1 Ant, accumulated 110-320 E_. co!1/g after 24 hours at
6-ll°C.
6.3.1.2. SALMONELLA — Fish and shellfish living 1n waters polluted
by waste discharges are commonly found to harbor Salmonella species
(Buttlaux 1962). Salmonellae are not known to cause disease 1n fish or
shellfish, but they do cause temporary Infection when the fish or shellfish
are residing 1n waters containing salmonellae. F1sh or shellfish can be
decontaminated by placing them In clean water, but salmonellae are
eliminated more slowly than E_. coll. Heuschmann-Brunner (1974) experimented
with carp and tench kept In water heavily contaminated with S. enter1t1d1s
and S. typh1mur1um. A few hours' residence In heavily polluted water caused
Infection, and salmonellae spread rapidly along blood and lymph vessels
throughout the body, Including the musculature. Salmonellae were
6-19
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found most often, and for the longest time, In the digestive tract. At
9-12°C, Salmonella Infection persisted 1n the tench gut for 60 days and In
the carp gut for 68 days.
Shellfish are often harvested from estuaries where polluted or poten-
tially polluted waters flow Into the sea. Salmonellae may be concentrated
1n the flesh of filter-feeding mollusks In the same manner as enterovlruses
and £. coll. Salmonellae are frequently Isolated from shellfish harvested
from contaminated waters and have given rise to major and many minor out-
breaks of salmonellosls and enteric fevers (Buttlaux, 1962). Depuration of
shellfish, by placing them 1n clean water, seems to be less effective 1n
removing salmonellae than In £. coll (Feachem et al., 1983).
Janssen (1974) took oysters (Crassostrea vlrglnlca) from the Chesapeake
>
Bay and kept them In an aquarium with salinity of 1.5% and water temperature
of 20°C. The oysters were exposed to artificial seawater containing 2xl07
S_. typhlmuM urn/100 ma for 48 hours and then kept 1n clean water
continually decontaminated by ultraviolet light. Oysters accumulated S.
typhlmurlum at a concentration of <2.8xlOVoyster and stm contained
170/oyster after 42 days 1n sterilized water. In other experiments 1n which
the depuration water was only Intermittently sterilized by ultraviolet
light, oysters excreted S.. typhlmurlum for 14 days and after 49 days still
contained 6000/mollusk. These rates of Salmonella elimination by oysters In
clean water are far slower than the reported rates for enterovlruses and £.
coll elimination (D161rolamo et al., 1975; Hoff and Becker, 1969).
Slanetz et al. (1968) studied salmonellae In water and oysters In an
estuary In New Hampshire. Water salinities were 1.1-2.5% and temperatures
were 8-26°C. Salmonellae were readily Isolated from water 1n which the
collform count was below the limit recommended for shellfish-growing waters
6-20
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(70/100 ma) and on two occasions were Isolated from shellfish that met the
conform standard (<230/100 g). On three occasions salmonellae were
Isolated from estuarlne waters and shellfish containing no fecal conforms.
Rowse and Fleet (1982) recently studied the survival of Salmonella
charity and E_. coll 1n oyster feces. They demonstrated that these organisms
are released 1n the feces and will survive at least 48 hours afterwards.
The salmonellae were eventually resuspended Into the overlying water from
the feces. Tonney and White (1925) reported that when cultured oysters were
kept 1n artificial seawater that contained 2x10° S. tvphlmurlurn/ma, and
stored at various temperatures, cells of S. tvphlmuMum were recovered for
60 days 1f the temperature was kept at 7.2°C. Similarly, Jordan (1925)
found that S. tvph1mur1um survived for 21-24 days when oysters were kept at
5-8°C. N1sh1o et al. (1981) reported that when oysters were stored at
-20°C, the viability of S. tvphlmurlum was apparently unaffected <140 days.
6.3.1.3. VIBRIO CHOLERAE — Outbreaks of V. cholerae have been traced
to shellfish grown In sewage-polluted waters (Blake et al., 1977). In
recent years several seafood-associated outbreaks of V. cholerae have
occurred along the U.S. Gulf Coast (DePaola et al., 1983). The organisms
(El Tor) have been reported to survive 1n fish for <16 days at 2.15°C
(Feachem et al., 1983). The El Tor blotype appears capable of surviving 1-2
weeks 1n fish and shellfish at 2-10°C (Feachem et al., 1983).
6.3.2. Viruses. Outbreaks of shellfish-associated enteric Illness 1n the
United States, Europe and Australia are well documented (Grohmann et al.,
1981; 6111 et al., 1983; Richards, 1985). While reported cases of bacterial
Illness from shellfish have decreased In the United States, cases of enteric
virus have Increased (Richards, 1985). Outbreaks associated with hepatitis,
6-21
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Norwalk virus and new unclassified enterovlruses have been documented. The
greatest risks of viral Infection are associated with the Ingestlon of con-
taminated mollusks (such as oysters, mussels, cockles and clams) and crusta-
cea (such as crabs, lobsters, shrimps and prawns) 1n a raw or partially
cooked state. Most attention has focused upon oysters because they are
commonly eaten raw and their method of filter feeding (common to all bivalve
mollusks) concentrates pathogenic organisms from the water Into their tis-
sues (Gerba and Goyal, 1978). Several studies have demonstrated the occur-
rence of enterovlruses 1n shellfish 1n areas far from the source of sewage
contamination (Gerba and Goyal, 1978). Goyal et al. (1984a) have Isolated
enterovlruses from rock crabs at both the New York Bight dump site and the
Philadelphia sewage sludge dump site.
Like bacteria, shellfish will accumulate viruses during feeding to num-
bers much greater than 1n the surrounding water. The viruses are concen-
trated mainly 1n the digestive system and may be present In concentrations
>100-fold higher than In the surrounding water (Gerba and Goyal, 1978).
Thus, It 1s not surprising that in many field studies in which they have
been Isolated from shellfish, no viruses have been detected In seawater from
the same location. For example, Metcalf and Stiles (1965, 1968) isolated
enterovlruses from oysters In estuarine waters at distances of <6.4 km from
the nearest sewage outfall, but no enterovlruses were detected in the
seawater at the same location.
It Is generally agreed that no human enterovirus multiplication takes
place In shellfish and that the dangers lie in the uptake, concentration and
survival of viruses 1n shellfish tissue. Uptake, depuration and survival in
oysters have been found to be temperature dependent. Below a given tempera-
6-22
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ture, a particular species of shellfish will cease to filter. Survival of
enterovlruses 1n shellfish appears to be much greater than 1n seawater.
Hedstrom and Lycke (1964) found that pollovlrus survived for 3.5 days In
seawater, but for well over 6 days In oysters In contaminated seawater.
Studies of polluted oysters In New Hampshire Indicated that no reduction In
virus tlter occurred for 30 days during winter when the water temperature
was ~1°C. During this time the oysters were probably dormant and not feed-
Ing (Hetcalf and Stiles, 1965). Survival of viruses In stored shellfish Is
very much prolonged by low temperatures (Gerba and Goyal, 1978). Studies of
viruses In refrigerated shellfish have shown that survival times of <120
days are possible.
6-23
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7. INFECTIVE DOSE FOR MICROORGANISMS
Important 1n any risk assessment Is the level of concentration of con-
taminant that 1s necessary to cause an adverse health effect. Ideally,
maximum contaminant levels for potentially harmful substances would be
established on firm ep1dem1olog1cal evidence where cause and effect can be
clearly quantified to determine a minimum- or no-risk level. However, while
epidemiology 1s a valuable tool for detecting patterns of risk and
establishing statistically significant associations with risk agents, 1t
cannot easily demonstrate cause and effect quantitatively (CST, 1983).
Exact data on minimum Infectious dose (HID) for humans are generally not
possible because of the extreme cost, unethical nature of human
experimentation and uncertainty 1n extrapolating dose-response curves to low
exposure levels.
Risk assessment can be divided Into four major steps: hazard Identifi-
cation, dose-response assessment, exposure assessment and risk characteriza-
tion (NRC, 1983). The continuing occurrence of outbreaks of viral hepatitis
and waterborne diseases by microorganisms 1n the United States clearly
demonstrates that a hazard exists from viral contamination of water.
An estimate of MID 1s extremely difficult. To obtain data that could be
used for the purpose of predicting the probability of Infection from low
numbers of microorganisms, large numbers of Individuals would be required
who would have to be exposed to a highly virulent microorganism. Even If
such experiments could be done, there would still be a great deal of
uncertainty when extrapolating dose-response curves to low exposure levels.
In addition, there are a number of other factors that would contribute to
7-1
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uncertainty In determining MID. A number of these factors are listed 1n
Table 7-1 along with an estimate of their contribution to uncertainty.
7.1. MINIMUM INFECTIVE DOSE
Ward and Akin (1984) recently reviewed the literature on HID of human
viruses In a limited number of healthy Individuals. The results Indicated
that relatively* low numbers of viruses, perhaps 1 or 2 tissue culture PFU,
were capable of causing Infection. It should be realized, however, that
Infection does not necessarily mean disease.
A number of studies have been published 1n which small numbers of
viruses, primarily vaccine strains, produced Infection 1n human subjects.
Koprowskl et al. (1956) fed pollovlrus 1 1n gelatin capsules to adult volun-
teers and Infected 2/3 subjects with 2 PFU of the virus. Katz and Plotkln
(1967) administered attenuated pollovlrus 3 (Fox) by nasogastrlc tube to
Infants and Infected 2/3 with 10 TCID,,n and 3/10 with 1 TCIDrrt of the
bu 50
virus. Minor et al. (1981) administered attenuated pollovlrus 1 vaccine
orally and Infected 3/6 Infants who were 2 months old with 50 TCID5Q of
the virus.
The most extensive studies to date on MIDs for enteric viruses have been
conducted by Schlff et al. (1984) and Ward and Akin (1984). Over 100
healthy adult volunteers were fed various doses of echovlrus 12, a very mild
pathogen, 1n drinking water. Using problt analysis, an estimated average
MID of 17 PFU was obtained.
The Infective dose of protozoan cysts also appears to be fairly low.
The Infective dose of 61ard1a lamblla and Entamoeba hlstolytlca by the oral
route appears to be between 1-10 cysts (Kowal, 1985). Essentially one
helminth egg can be considered to be Infectious, although symptoms may be
dose related (Kowal, 1985).
7-2
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TABLE 7-1
Contributors to Uncertainty In Determining
Minimum Infectious Dose for Enteric Viruses*
Category
Contribution to Uncertainty
1. Determination of Immune status
2. Assay technique
3. Sensitivity of host
4. Virulence of virus
5. Use of upper 95% confidence Umlt
6. Route of exposure
7. Choice of dose-response model
8. Synerglsm/antagonlsm
9. Dietary considerations
10. Distribution of subjects among
doses and number used
One order of magnitude
One order of magnitude
Several orders of magnitude
Several orders of magnitude
Up to one order of magnitude
One order of magnitude
Several orders of magnitude
Many orders of magnitude
Uncertain
1-2 orders of magnitude
*Source: Gerba, 1984
7-3
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HIDs for bacteria are generally higher than that for viruses and para-
sites. The number of Ingested bacteria necessary to cause Illness appears
to range from 102-108 (Akin, 1983). However, more recent studies sug-
gest that the Infective dose for Salmonella bacteria may be <10 organisms
(D'Aoust, 1985). Virulence of the particular type and strain of organism as
well as host factors may play a role 1n the actual number of organisms
required to cause Infection. D'Aoust (1985) has suggested that the MID of
Salmonella bacteria may be much less when present 1n certain types of food,
such as cheese.
Unlike risks associated with toxic chemicals 1n water, Individuals who
do not actually consume or come Into contact with contaminated water or
sludge are also at risk. This 1s because microorganisms may also be spread
by person-to-person contact or subsequent contamination of other materials
with which nonlnfected Individuals may come into contact. This secondary
and tertiary spread of microorganisms has been well documented during
waterborne outbreaks of Infection caused by the Norwalk virus (Gerba et al.,
1985). In the case of Norwalk outbreaks, the secondary attack rate Is ~30%
(Figure 7-1). The recent discovery of viable but nonculturable bacterial
pathogens (Xu et al., 1982; Colwell et al., 1985) should also be recognized
1n any discussion on Infective dosage and relative risks. Extensive
microcosm and field studies have Indicated that all bacteria entering
natural waters may not die off and that some may persist 1n a dormant
state. These organisms, however, are Incapable of growth 1n conventional
culture media. Thus, Colwell et al. (1985) observed that direct viable
counts of bacteria were consistently higher by eplfluorescent microscopy
than by corresponding plate counts. A water source may, therefore, be found
to be bacterlologlcally acceptable on direct plate count of bacteria but may
7-4
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stm harbor viable, nonculturable bacteria that may be potentially
virulent. Obviously, there 1s need for studies on the
vlrulence/pathogenlclty of such microorganisms.
7.2. ESTIMATED MORBIDITY AND MORTALITY FOR ENTERIC PATHOGENS
Not everyone who may become Infected with enteric viruses or parasites
will become clinically 111. Asymptomatic Infections are particularly common
among some of the enterovlruses. The development of clinical Illness
depends on numerous factors, Including the Immune status of the host, age of
the host, virulence of the microorganism, type, strain of microorganism and
route of Infection. For hepatitis A virus, the percentage of Individuals
with clinically observed Illness is low for children (usually <5%) but
Increases greatly with age (Figure 7-2). In contrast, the frequency of
clinical symptoms for rotavlrus 1s greatest 1n childhood (Gerba et al.,
1985) and lowest 1n adulthood. The observed frequencies of symptomatic
Infections for various enterovlruses are shown 1n Figure 7-3. While the
frequency of clinical hepatitis A virus in adults 1s estimated at 75%,
during waterborne outbreaks 1t has been observed to be as high as 97%
(Lednar et al., 1985).
Mortality rates are also affected by many of the same factors that
determine the likelihood of the development of clinical illness. The mor-
tality rate for salmonellosls In the United States Is 0.2% and shlgellosis
0.13% (Berger, 1986). The risk of mortality for hepatitis A virus is 0.6%
(CDC, 1985). Mortality for hepatitis A virus is 1.4% for hospitalized cases
and 0.3% for nonhospitalized cases. Mortality from other enterovirus Infec-
tions has been reported to range from <0.1-1.8% (Assaad and Borecka, 1977).
Mortality rates for enteric bacteria and enterovlruses are summarized in
Table 7-2. The values for enterovlruses probably only represent hospital-
ized cases.
7-6
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TABLE 7-2
Mortality Rates for Enteric Bacteria and Enterovlruses*
Organism
Mortality Rate
(X)
Salmonella
Shlgella
Hepatitis A
Coxsackle A2
A4
A9
A16
0.2
0.13
0.6
0.5
0.5
0.26
0.12
Coxsackle B
Echo 6
9
Polio 1
0.59-0.94
0.29
0.27
0.9
*Source: Assaad and Borecka, 1977; CDC, 1985; Berger, 1986. Data for polio,
coxsackle and echo probably represent only hospitalized cases.
7-9
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8. SETTLING AND DISPERSAL OF SLUDGES DURING DISPOSAL
Transport of sludge particles and sludge-associated pathogens 1s Influ-
enced by site-specific physical and meteorological conditions such as depth,
wind-Induced waves and currents, geostrophlc flow and density gradients
(temperature and salinity stratifications). A large portion (~70-80%) of
the remaining sludge stays 1n suspension and 1s dispersed along density
gradients. The degree of sediment accumulation 1s a function of Input
volume, particle size and "flush-out" rate of a site by currents and of
decomposition of the organic matter.
Because the sludge partlculates have a density greater than that of sea-
water, they must eventually sink and may be Incorporated Into sediments.
The settling rate of sludge 1n the ocean, fraction of sludge held 1n
suspension and the amount of sludge that sinks Immediately to the bottom
following dumping are not known precisely. It has been reported that when
seawater and sludge are gently mixed, large floccules of sludge are formed,
which have a density greater than seawater. According to Jenklnson (1972),
sinking alone would account for the appearance of sludge 1n 23 m of water 20
minutes after dumping commences.
The thermocllne retards the rate of downward mixing of the wastewater
sludge-seawater mixture as demonstrated by Increased concentration of the
sludge at depths below 17 m for >2.5 hours after dumping (Duedall et al.,
1975).
The rapid descent of sludge 1s thought to be due to a combination of
processes, Including the rapid settling rate of heavier sludge fractions,
the Initial momentum of sludge "jets" as the sludge leaves the dumping
vessel, the formation of large floccules with high settling velocities and
8-1
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the lack of thermocllne 1n the upper water column (Duedall et al., 1977).
In a study at the Philadelphia dump site, Lear et al. (1977) suggested that
sludge may be settling 1n topographic depressions of the ocean floor and
concluded that a portion of the sludge may accumulate at the site while the
remaining portion disperses away from the site.
It should be pointed put that primary sludge 1s usually heavier and will
settle faster than secondary sludge. Duedall et al. (1977) found that a
discharge of 2890 m3 of sludge over a 9-m1nute period resulted 1n the
formation of a plume of 200-250 m diameter within 10-15 minutes after the
discharge event. The surface plume remained visibly Ink black for ~30
minutes and then drifted In a southeast direction. Also, the patch had
drifted 1.5 km from the Initial point of discharge when the scientists left
the sludge dump.
8.1. SHALLOW DUMP SITES
Sludge dumping may not only have the potential to contaminate the actual
dump site but also the surrounding areas. Bablnchak et al. (1977) found
that sewage sludge material had contaminated areas extending 11 km north and
37 km south from the New York Bight dump site. These results were based on
the densities of fecal-coHforms 1n sediments. If fine sediment and sludge
particles become burled by the process of sedimentation, then the pathogens
will probably be "locked up" and may not reenter the system. However, 1f
these fine sediments are rolled up by waves during storms, then they move,
sometimes hundreds of kilometers, before settling to the bottom again
(Squires, 1983).
Limited Information Is available on the dilution rate of pathogens 1n
relation to distance from the center of a dump site. O'Malley et al. (1982)
reported the frequency of Isolation of total conforms, fecal conforms,
8-2
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fecal streptococci and amoebae in sediment samples by distance from the
Philadelphia dump site. A decrease 1n the percentage of positive stations
for total conforms and fecal conforms was observed with Increasing
distance from the center of the dump site. Assuming a linear rate of
disappearance, this decrease In conform occurrence may be estimated to ,be
an average of 3 and 2%/km for total conforms and fecal conforms,
respectively. Beyond a distance of -19-23 km, a slight Increase In the
percentage of positive stations for total conforms and fecal conforms was
noted. The range of recovery of Indicator bacteria extended 37 km northeast
and 37 km southwest, between the 40- and 70-m Isobaths. The total area in
which organisms originating from the disposal activities were recovered was
estimated at 1190 km2. Site-specific conditions such as wind-Induced
currents and transport of water masses have been suggested as possible
mechanisms for the Irregular long-range distribution of the
sludge-associated bacteria. No details were given, in the cited study, of
the actual counts of bacteria in the sediment samples except for a general
range of 10-2400 MPN/100 g sediment for both total conform and fecal
conforms.
A rapid decrease 1n the percentage of stations yielding samples positive
for total conforms and fecal conforms, above and below a certain concen-
tration, with increasing distance from the dump site was also reported In.a
recent study at the New York Bight (Davis and Olivleri, 1984}. An increase
in the frequency of positive stations for total conforms and fecal
conforms near the shore apparently resulted from anthropogenic sources
other than sludge from the dump site. In the same study, an exponential
decrease of 2 orders of magnitude 1n total conform count was observed along
a transect of -20 km from the New York Bight dump site to the shore (Davis
8-3
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and Ollvlerl, 1984). Based on a mathematical model for the ocean dumping of
sludge at the New York Bight site, a Ixl0«-5xl0«-fold dilution within 4
hours following disposal was predicted (NYC-DEP, 1983) and, 1n fact, was
confirmed for total conforms and fecal conforms at the site (Davis and
Ol1v1er1, 1984).
The only direct evidence of recovery of sludge-associated pathogens
comes from a study by Goyal et al. (1984a), who Isolated enterovlruses from
samples of water, sediment and crabs 1n the vicinity of the Philadelphia and
New York Bight dump sites. According to this study, the highest recovery of
enterovlruses was In sediment samples. In water samples, enterovlruses were
recovered only once (out of 37 samples). This result suggests that most of
the dumped sludge settles quickly to the bottom of the ocean and forms a
part of the sediment (Jenklnson, 1972). The sediment can then play a major
role 1n the transport and distribution of the sludge-associated pathogens In
the marine environment. Other studies have also shown that the concentra-
tion of viruses 1n the sediments 1s much higher than In the overlying water,
and that sediment viruses survive longer than those free 1n suspension
(Gerba et al., 1977; LaBelle and Gerba, 1982). Because the amount of sludge
dumped Into the ocean Is small 1n relation to the volume of the receiving
water, the probability of Isolation of a virus from water 1s very low.
However, density gradients may be an exception and permit viruses to be
locally concentrated.
As 1n the cases of bacterial studies mentioned above, most of the sta-
tions positive for viruses were located 1n and several kilometers around the
dump sites (Goyal et al., 1984a). Enterovlruses were also recovered well
away from the center of the dump sites (actual distance not reported).
8-4
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8.2 106-MILE DEEP WATER SITE
The 106-mne deep water site 1s beyond the continental shelf, over
portions of the continental slope and continental rise. The topographically
rugged northwest corner of the site overlies the continental slope that Is a
subsea drainage network of canyons, gullies and chutes. This area Is
characterized by .an ~4% grade, while the relatively flat southeast corner,
the continental rise region of the site, has only a 1% grade (NOAA, 1977)
and Includes meandering channels, eroslonal scan and debris aprons. Water
depths at the site range from 1440 m 1n the northwest corner to 2750 m In
the southeast corner. The continental slope and rise 1n this region Is a
deposltlonal environment with localized sites of sediment denudation.
Formations that are turned landward beneath the continental shelf can be
traced seaward to outcrops along the mid and lower slope. Middle and late
Eocene strata crop out at depths between 1600 and 2000 m 1n the northwest
corner of the 106-mile site. In 1975-1976 14 dives were made at the site
with the submersible Alvln (Ryan and Farre, 1983). Observations of the
topography ranged from "flat bottom, gray sllty clay with no ripple marks
(2440-2477 m)" to "partly flat and partly steep; some ripple marks; rounded
hillocks and outcrops of modular sediments, gravel, cobble, and occasional
sponges and warm tubes." At the base of Berkley Canyon, the terrain Is
dissected by gullies 2-12 m across and up to 15 m deep. The occurrence of
numerous boulders on pale grey sediment was reported on several dives. The
sediment base is a grey silty and sandy clay that has been heavily reworked
by benthic organisms. Holes and mounds formed by animals are common.
Attached epifauna such as sponges, anemones and octocorrals occur on many
hard outcrops. Containers and allochthonous material were reported on
several different occasions.
8-5
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The water column at the site 1s Influenced by three major water masses:
shelf water, slope water and Gulf Stream water. Vertical density
stratification of the water column has an Important effect on site
hydrodynamics. A seasonal pycnocllne commonly occurs from May to September
at a depth of ~20 m and a permanent pycnocllne exists ~100 m deep. The mean
direction of flow at the site Is southwest along the shelf/slope boundary.
Off the coast of Cape Hatteras, this southwesterly flow turns
counterclockwise and proceeds northeast with the flow of the Gulf Stream.
Water velocities are roughly 11 cm/sec 1n the mixed upper layer (Ingham,
1981) and -2.5-5.0 cm/sec 1n deeper waters (Paul, 1983).
A major feature 1s that of warm-core Gulf Stream eddies. Eddies may
remain relatively Intact and follow a path that parallels the shelf contour
southward until they rejoin the Gulf Stream north of Hatteras. When an eddy
of 100 km diameter 1s within the 106-mile site, 1t remains so for ~3 weeks
(B1sagn1, 1976). The overall effect of eddies 1s to alter the short-term
flow structure, but they do not change long-term dispersive characteristics
at the site (O'Connor et a!., 1983). Typical of the East Coast 1s a front
between slope and shelf water. This front 1s not static but may Inhibit
movement of water onto the shelf. Ingham (1981) estimated that shelf water
encompassed at least part of the 106-mile site for 32% of the time from
October 1979 to September 1980. Csanaday (1983) noted that the seaward
salinity gradient implies a net eastward movement of cold, fresh shelf water
to the warm, more saline Sargasso Sea.
The interaction of the three major water masses (shelf, slope, Gulf
Stream) and the stratification that occurs 1n summer present a complex
picture. The seasonal pycnocllne changes as a function of time because of
the dally seasonal variability of heating of the mixed layer and the passage
8-6
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of atmospheric storms and frontal systems of varying Intensity (Orr and
Baxter, 1983). Internal waves may displace the pycnocllne several meters or
more. Acoustic backscattering was used to study the fate of plumes from
add/Iron wastes and sewage sludge at the 106-mile site 1n Guly 1977 and
February and April 1978. During the spring and summer months, the density
structure at the base of the mixed layer limited the vertical penetration of
particles. The data show an order of magnitude difference 1n temporal
dependence of plume width as a function of season. Plume width broadens
quickly 1n summer and springtime and remains narrow during wintertime water
conditions. Plumes penetrate deeper in winter because of the absence of a
shallow pycnocllne, but they are not always uniformly distributed 1n the
vertical plane. The effect of a warm eddy was seen in July 1977, when a
sewage sludge plume was advected almost 56 km eastward 1n 24 hours (Orr and
Baxter, 1983). O'Connor et al. (1983) described the flux of water through
the dump site as a river-like flow 20 m deep in summer, at least 60 km wide,
traveling to the southwest with an average velocity of 11 cm/sec.
8-7
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9. QUALITATIVE RISK ASSESSMENT
Insufficient Information is available to perform a quantitative risk
assessment for ocean disposal of municipal wastewater sludge. However, a
qualitative discussion of risk from ocean disposal of sludge is provided in
this section. It should be noted that of the three exposure pathways
discussed, the marine food risk assessment (Section 9.1) is the only pathway
with potential applicability for deep water sites.
9.1. MARINE FOODS RISK ASSESSMENT
Perhaps the greatest potential risk associated with the disposal of
municipal wastewater sludges in the open ocean is the entrance of bacterial
and viral organisms into seafood meant for human consumption. As discussed
in previous chapters, enteric viruses and bacteria are capable of surviving
for years in sediments contaminated with sewage sludge. Field studies have
already shown that these organisms have gained entrance into seafood at both
the New York Bight and the Philadelphia dump sites. They have been found in
shellfish and other marine organisms that are harvested commercially. They
have also been found in crabs, which may migrate long distance's from the
site where they were exposed to the pathogenic microorganisms. Consumption
of these marine organisms poses a potential risk to consumers. Documented
shellfish-associated outbreaks of viral hepatitis and gastroenteritis are
currently on the increase in the United States (MMWR, 1982). Even the
presence of low numbers of some pathogenic enteric microorganisms may pose a
significant risk. Because of the extended survival of enteric bacteria and
viruses in marine sediments and marine organisms, these risks persist for
years after the disposal of the sludge.
9-1
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Besides risks associated with direct disease transmission from consump-
tion of contaminated marine organisms, sludge dumping may encourage the
growth of native marine bacterial pathogens such as y. cholerae and the
transmission of antibiotic-resistant organisms.
Recently 1t has been shown that food can play a role 1n the transmission
of antibiotic-resistant bacteria and associated diseases. It has been
demonstrated that antibiotic-resistant enteric bacteria can persist for at
least 4 years at the Philadelphia dump site. These organisms are
undoubtedly serving to contaminate shellfish and other marine foods.
For shallow water dump sites, it is evident that a measurable risk of
disease transmission by marine foods is associated with sludge-dumping
activities. Because of the association of pathogens with sediments, and
because shellfish live very close to sediments, the risk of bloconcentration
of pathogens by shellfish should not be overlooked. However, if the area 1s
closed to shellfish harvesting, this route of exposure may not be
Important. Over 39% of New Jersey and Long Island coastal waters are
currently closed to shellfishing.
9.2. AEROSOL PATHWAY RISK ASSESSMENT
Ocean disposal of sludges produces aerosols containing enteric
microorganisms present In the sludge. Discharge of the sludge to the ocean
surface also results in wave action. Previous studies have demonstrated
that bubbles produced by wave action act to attract both enteric bacteria
and viruses to their surfaces, subsequently ejecting them into the overlying
air mass (Baylor et al., 19773,b). Bubble levitation can produce aerosols
containing 200-1000 more microorganisms/volume than the water mass from
which they were produced. Marine microorganisms have been detected in air
as far as 160 km inland, suggesting long-distance transport of
marine-generated aerosols (Baylor and Baylor, 1980). Enteric bacteria and
9-2
-------
viruses may be transmitted by inhalation of aerosols or by contact with
surfaces that have been exposed to aerosols {Feachem et al., 1983). The
Infectious dose of enteric microorganisms may actually be less by the
respiratory than by the oral route as suggested by the studies of Crozier
and Woodward (1962).
Studies have been performed on the potential generation of infectious
aerosols during activated sludge treatment and during the land application
of sewage by spraying (Pahren and Jakubowski, 1980). Aerosols containing
measurable levels of enteric organisms can be found near both of these
treatment methods; however, no measurable health effects have been observed
(Pahren and Jakubowski, 1980; Feachem et al., 1983). Although bubbles tend
to concentrate microorganisms, air currents probably result in rapid
dilution of the microorganisms. In addition, factors such as sunlight and
dessication act to enhance microbial die-off. The concentration of enteric
organisms a few moments after sludge disposal in the ocean 1s far less than
that occurring in sewage effluents. Thus, the concentration of enteric
organisms in aerosols after sludge dumping is less than that observed at
activated sewage treatment plants. Because aerosols can travel for several
miles and because infective dose by inhalation is much less than by
1ngest1on, the aerosol pathway (although it should not be considered
trivial) is an Insignificant route of infection, particularly at the
106-mile deep water site.
9.3. CONTACT EXPOSURE RISK ASSESSMENT
As previous epidemlological studies have demonstrated at shallow water
dump sites, a measurable risk of disease transmission exists from bathing 1n
fecally contaminated marine waters (Cabelli, 1983). Thus, it is conceivable
that a risk does exist if bathers or divers come into contact with marine
waters as a result of sludge dumping. It 1s known that much of the sludge
9-3
-------
material drifts to areas outside of disposal sites located along the
Atlantic coast (Cabelll and Pedersen, 1982; Goyal, 1984). A review of the
literature suggests that sludge disposed 1n the New York Bight Is most
likely to have an Impact on coastal marine bathers. Microorganisms present
1n sludge at the Philadelphia and 106-mile sites are highly unlikely to
reach coastal bathing areas 1n any significant concentrations given transit
times and dilution. Using the presence of C1ostr1d1um per.fr Ingens spores In
sediments, Cabelll and Pedersen (1982) found that no significant
concentration of spores above background levels was likely to reach coastal
bathing areas. In another study on gastroenteritis 1n the New York Bight,
they also suggested that there was no observable Impact on occurrence of
gastroenteritis among bathers that could be attributed to sludge dumping
(Cabelll, 1982). However, It should be pointed out that these recreational
areas are already Impacted by sewage contamination from sewage outfalls and
the Hudson River. As the previous studies have shown, this contamination
does affect the health of marine bathers. This background contamination
actually prevented researchers 1n the two previously cited studies from
making a more quantitative assessment. Even 1f the background contamination
had been lower or not present, some Impact might have been observed. But,
1t would appear certain that 1t would not likely have exceeded that already
present.
In summary, there 1s currently no obvious evidence that sludge dumping
at sites 1n the North Atlantic has an Impact on bathers at marine beaches.
However, 1f microorganisms present 1n sludge reach bathing beaches, a person
using these areas could be exposed to a health risk.
In addition to marine bathers, recreational and commercial divers would
also be at risk of Illness 1f they conducted activities 1n areas Impacted by
the sludge. Because of greater contact with the water, they would be
9-4
-------
expected to be at greater risk. As discussed 1n Chapter 8, the sewage
sludge 1s dispersed over large areas outside of the dump site area.
Elevated densities of fecal Indicators have been found as far as 105 km (65
miles) from sludge dump sites (Cabelll and Pedersen, 1982), suggesting that
risks to divers may extend over large areas. Obviously, the contact
exposure pathway 1s more Important 1n coastal, estuaHne and brackish waters
because of their use for water contact sports.
The literature review suggests that enteric bacteria and viruses are
capable of surviving for years 1n sediments, at least at one dump site. For
the conditions at the Philadelphia dump site using the die-off model
developed by Hejkal and Gerba (1982), H was estimated that the t 1n the
sediment was 476 days (table 9-1). The time required for the total
1nact1vat1on of all the viruses dumped, If they became sediment associated
with the Philadelphia site in 1980, would be In excess of 9 years (Table
9-2). Using the model described by Mandni (1978), the survival of
conforms in seawater would be 12 days at 6°C and 10 days at 10°C. However,
while coliform survival may seem rather rapid, 1t must be remembered that
the data used to develop the model were for freely suspended conforms and
not sludge-associated conforms. Sludge can be expected to have a major
effect on the survival of conforms in marine waters. Unfortunately, no
studies have been conducted on sludge-associated enteric organisms in marine
waters. This information would be essential for a proper risk assessment
for it is evident from field studies that conforms can persist for years in
sludge-contaminated marine sediment.
9-5
-------
TABLE 9-1
Estimated Die-Off Rates of Enteric Viruses 1n Seawater,
Sediments and Shellfish at Various Temperatures3
Time In Days for 90 and 99%
Virus Inact1vat1on
Temperature
6
10
15
20
Log-jQ Virus
Inactivated
per Dayb
0.017
0.15
0.32
0.65
Seawater
tgo tgg
59 118
7 14
3 6
1.5 3
Sediments
and Shellfish
tgo 199
236 476
28 56
12 24
6 12
aSource: Hejkal and Gerba, 1982
bLog-|Q/day = -0.184 + 0.0335 (temperature °C)
9-6
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10. SUMMARY AND CONCLUSIONS
The purpose of this document was to Identify human pathogens associated
with sewage sludge and the potential risks posed by them following the ocean
dumping of municipal wastewater sludge. Background Information on pathogens
of concern and their persistence 1n marine environments has been presented.
Attempts have also been made to Identify different routes by which pathogens
can reach humans and to qualitatively discuss risks associated with each of
the potential routes.
Because of a limited number of studies on the pollution of marine
environments by sludge disposal, 1t 1s difficult to assess these risks. It
1s known that pathogens can persist 1n sediments for an extended period of
time and that animals (for example, rock crabs) dwelling at a dump site can
pick up these organisms and move away from the site. It 1s also known that
sludge-Impacted sediments can drift long distances from the point of
discharge. Whether these sediments and their associated pathogens can reach
coastal environments does not seem likely under normal conditions, but In
the event of storms and quakes 1t Is a distinct possibility. It 1s logical
to assume that this pollution 1s less likely to happen when sludge 1s
disposed at the 106-mile site than at the New York Bight or Philadelphia
dump sites because of the distances Involved.
Predictions on viral and bacterial decay following ocean disposal of
sludge will require Information on the vertical and horizontal movement of
discharged sludge as well as on the survival of pathogens attached to sludge
particles. The latter Information 1s not currently available. Studies on
how far aerosols can travel and how long pathogens can survive 1n them are
also Incomplete. Obviously, consumption of seafood from 1n and around a
10-1
-------
shallow water dump site Is riskier to health than swimming because of the
bloconcentratlon of pathogens by filter feeders.
In summary, with what Uttle Information is available, it Is only
possible to speculate on the occurrence of human health risks from pathogens
In municipal sludge disposed 1n the ocean. More research 1s needed in order
to develop a definitive risk assessment methodology.
10-2
-------
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